Apparatus and method for transmitting muting information, and apparatus and method for acquiring channel state using same

ABSTRACT

The present disclosure relates to an apparatus and a method for transmitting muting information in a wireless communication system, and to an apparatus and a method for acquiring channel state using same. In an exemplary embodiment, muting information includes: a first data field, having a serving cell for receiving from peripheral cells in a multi-cell environment, at least one of a CSI-RS pattern, the number of CSI-RS antenna ports, a CSI-RS duty cycle, and CSI-RS transmission subframe offset information, and using same for expressing the cycle and the offset of muting subframes, which pertain to information on a resource block that can generate interference between the peripheral cells and CSI-RS; and a second data field for expressing a specific muting pattern, which must be muted within the muting subframes, having either 12 bits or 28 bits that display muting application in a bitmap format.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the National Stage Entry of InternationalApplication No. PCT/KR2011/005919, and claims priority to Korean PatentApplication No. 10-2010-0077590, filed on Aug. 11, 2010, Korean PatentApplication No. 10-2010-0078536, filed on Aug. 13, 2010, Korean PatentApplication No. 10-2010-0098005, filed on Oct. 7, 2010, and KoreanPatent Application No. 10-2010-0098006, filed on Oct. 7, 2010, all ofwhich are incorporated herein by reference as if fully set forth herein.

BACKGROUND

1. Field

The embodiment of the present invention relates generally to a wirelessis communication system, and specifically to a method and an apparatusfor performing muting for all or a partial resource region in a resourcespace (PDSCH, Physical Downlink Shared Channel) for data transmission ofa serving cell so as to avoid interference from a neighboring cell atthe time of allocating a resource of a channel stateinformation-reference signal (hereinafter referred to as “CSI-RS”) in awireless communication system, and using muting information for muting.

2. Discussion of the Background

As a communication system develops, consumers such as enterprises andindividuals come to use a wide variety of wireless user equipments.

The current mobile communication system takes an advance from a servicemainly devoted to a sound to a communication system with high speed anda large capacity that can transmit/receive various data such as videos,wireless data. A technical development for transmitting data with alarge capacity equivalent to a wired communication network is in demand,and a proper method for detecting an error which can improve systemperformance by minimizing the decrease in information loss andincreasing the efficiency in system transmission becomes an essentialelement.

In addition, in various current communications system, various referencesignals have been used for providing a counterpart apparatus withinformation on a communication circumstance or the like, through uplinkand downlink.

For example, in an LTE system, which is one of a mobile communicationmethod, a reference signal or a CRS (Cell-specific Reference Signal),which is a reference signal, is transmitted per subframe for identifyingchannel information at the time of downlink transmission.

At this point, a CRS is differently allocated and transmitted accordingto time/frequency with respect to each 4 antennas, according to 4, whichis the maximum number of antenna ports supported at downlink of an LTEsystem.

A next generation communication technology under development such asLTE-A may support up to 8 antennas for downlink. Accordingly, a CRSwhich is currently defined only for 4 antennas has a limit foridentifying channel information at the time of downlink transmission.Therefore, a reference signal, called as a CSI-RS (Channel StateInformation-Reference Signal; hereinafter referred to as ‘CSI-RS’), hasbeen newly defined for identifying channel state information for up to 8antennas.

In other words, a communication system using up to 8×8 multiple-inputmultiple-output (MIMO) antennas for both the transmitter and thereceiver is under discussion. Further, a user equipment should transmitdifferent CSI-RSs per respective antenna ports or layersreceiving/transmitting signals. However, while a basic definition andoverhead for a CSI-RS are currently being defined, a method forallocating and transmitting a corresponding CSI-RS pattern to eachresource region per antenna/base station (cell) and transmitting thecorresponding CSI-RS pattern has not yet been specifically defined.

Especially, in a communicating environment where one user equipmentshould receive CSI-RSs from various base stations or cells, it is likelythat intervention between CSI-RSs from different neighboring cells willoccur. Therefore, this situation should also be considered.

SUMMARY

An aspect of the present invention is to provide an apparatus and amethod for transmitting and receiving CSI-RSs by allocating the CSI-RSto time-frequency resource region per antenna ports.

Another aspect of the present invention is to provide a technology ofmuting so that data is not transmitted to a CSI-RS allocate resourceregion of another cell when resources of CSI-RSs are allocated for eachcell.

Another aspect of the present invention is to provide a technology fortransmitting and receiving muting information by generating the mutinginformation indicating a data muting region at the time of transmittingCSI-RSs.

Another aspect of the present invention is to provide a technology fortransmitting and receiving muting information by generating the mutinginformation indicating a muting region to which data is not allocated atthe time of resource allocation of the corresponding cell inconsideration of one or more of a CSI-RS pattern, the number of CSI-RSantenna ports, a CSI-RS transmission cycle (duty cycle), CSI-RStransmission subframe offset information of a neighboring cell.

Another aspect of the present invention is to provide a technology fortransmitting muting information, and transmitting and receiving CSI-RSsbased on the muting information by allocating resources of the CSI-RSsothat data is not transmitted to the muting region.

Another aspect of the present invention is to provide a technology forestimating and acquiring a channel state by receiving mutinginformation, and performing decoding in consideration of a muting regionbased on the muting information.

Technical Solution

In accordance with an aspect of the present invention, there is provideda method for transmitting muting information reflecting CSI-RSintervention of a neighboring cell by a specific cell in a multicellenvironment, the method including: receiving CSI-RS information of theneighboring cell including one or more of a CSI-RS pattern, the numberof CSI-RS antenna ports, a CSI-RS transmission cycle (duty cycle), andCSI-RS transmission subframe offset information, from the neighboringcell; determining a muting region which is a time/frequency resourceregion that overlaps with CSI-RSs of the neighboring cell and thereforerequires muting based on the CSI-RS information of the neighboring cell;generating the muting information including a first data field thatindicates a cycle and an offset of muting subframes, each of whichincludes the muting region, and a second data field that indicates aspecific muting pattern in which muting is to be performed in the mutingsubframes and has one bit number among 12 bits to 28 bits, whichindicates, in a bitmap format, whether to apply muting, and transmittingthe generated muting information to the user equipment.

In addition, in accordance with another aspect of the present invention,there is provided a method for acquiring a channel state of each cellafter receiving CSI-RSs from two or more cells by a receiver, the methodincluding: receiving muting information including a first data fieldthat indicates a cycle and an offset of muting subframes from a servingcell out of two or more cells and a second data field that indicates aspecific muting pattern in which muting is to be performed in the mutingsubframes and has one bit number among 12 bits to 28 bits, whichindicates, in a bitmap format, whether to apply muting; receivingCSI-RSs of the neighboring cell transmitted from a resource region of aneighboring cell corresponding to a partial region muted based on themuting information in a resource space for transmitting CSI-RSs of theserving cell and data of the serving cell; identifying a muting regionin a resource space for transmitting data of the serving cell using themuting information and identifying a region for transmitting CSI-RSs ofa neighboring cell corresponding thereto; and acquiring a channel stateby decoding CSI-RSs of the serving cell and the neighboring cellconsidering the muting region.

In addition, in accordance with another aspect of the present invention,there is provided an apparatus for transmitting CSI-RS mutinginformation, including: a neighboring cell information receiver thatreceives, from one or more neighboring cells in a multicell environment,CSI-RS information of the neighboring cells including at least one ofCSI-RS patterns, the number of CSI-RS antenna ports, CSI-RS transmissioncycles (Duty Cycle), and CSI-RS transmission subframe offsetinformation; a muting region determining unit that determines a mutingregion which is a time/frequency resource region that overlaps withCSI-RSs of the neighboring cell and therefore requires muting in aresource space for transmitting data of a serving cell based on theCSI-RS information of the neighboring cell; a muting informationgenerating unit that generates muting information including a first datafield which indicates the muting region and indicates a cycle and anoffset of muting subframes and a second data field which indicates aspecific muting pattern to be muted in the muting subframes and has onebit number among 12 bits to 28 bits, which indicates, in a bitmapformat, whether to apply muting; and a muting information transmitterthat transmits the generated muting information to a user equipment(UE).

In addition, in accordance with another aspect of the present invention,there is provided an apparatus for acquiring a channel state, theapparatus including: a muting information receiver that receives mutinginformation including a first data field that indicates a cycle and anoffset of muting subframes from a serving cell out of two or more cellsand a second data field that indicates a specific muting pattern inwhich muting is to be performed in the muting subframes and has one bitnumber among 12 bits to 28 bits, which indicates, in a bitmap format,whether to apply muting; a CSI-RS receiver that receives CSI-RS signalsof the neighboring cell transmitted from a resource region of aneighboring cell corresponding to a partial region muted based on themuting information in a resource space for transmitting CSI-RSs of theserving cell and data of the serving cell; a muting region identifyingunit that identifies a muting region in a resource space fortransmitting data of the serving cell using the muting information andidentifies a resource region for transmitting CSI-RSs of a neighboringcell corresponding thereto; and a channel state acquiring unit thatacquires a channel state by decoding CSI-RS signals of the serving celland the neighboring cell considering the muting region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram schematically illustrating a wireless communicationsystem to which an embodiment of the present invention is applied;

FIGS. 2 to 13 illustrate representative examples for mapping CSI-RSs toone subframe. FIGS. 2 to 5 illustrate CSI-RS patterns which arebasically applied to all of FS1 (FDD) and FS2 (TDD) and which are forthe case of a normal CP. FIGS. 6 to 9 illustrate CSI-RS patterns whichare basically applied to all of FS1 (FDD) and FS2 (TDD) and which arefor the case of an extended CP. FIGS. 10 to 13 illustrate examples ofCSI-RS patterns applied to FS2 (TDD) as additional options. FIGS. 10 and11 are cases of normal CPs, and FIGS. 12 and 13 are cases of extendedCPs;

FIG. 14 illustrates a multicell environment to which the presentembodiment is applied;

FIG. 15 illustrates a flow of a method of transmitting CSI-RS mutinginformation according to the present embodiment;

FIG. 16 is a flowchart illustrating a detailed configuration for stepsof generating muting information in the present embodiment;

FIG. 17 is a flowchart illustrating a method of acquiring channelinformation in a user equipment using muting information according tothe present embodiment;

FIG. 18 is a block diagram illustrating a CSI-RS muting informationtransmission apparatus according to the present embodiment;

FIG. 19 illustrates an example of a data format of muting informationaccording to the present embodiment;

FIG. 20 is a diagram illustrating a configuration of frames and resourcespaces indicating a state in which CSI-RSs of the actual serving cell ismuted based on muting information of FIG. 19;

FIG. 21 is a diagram illustrating a configuration of a channel stateacquiring apparatus using muting information according to the presentembodiment;

FIG. 22 is a flowchart illustrating a detailed configuration relating tosteps of is generating muting information according to anotherembodiment of the present invention;

FIG. 23 is a flowchart illustrating a method for acquiring channelinformation in a user equipment using muting information according to anembodiment of FIG. 22; and

That is, FIG. 24 illustrates an example of data format of mutinginformation according to an embodiment of FIG. 22.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription, the same elements will be designated by the same referencenumerals although they are shown in different drawings. Further, in thefollowing description of the present invention, a detailed descriptionof known functions and configurations incorporated herein will beomitted when it may make the subject matter of the present inventionrather unclear.

In addition, terms, such as first, second, A, B, (a), (b) or the likemay be used herein when describing components of the present invention.Each of these terminologies is not used to define an essence, order orsequence of a corresponding component but used merely to distinguish thecorresponding component from other component(s). It should be noted thatif it is described in the specification that one component is“connected,” “coupled” or “joined” to another component, a thirdcomponent may be “connected,” “coupled,” and “joined” between the firstand second components, although the first component may be directlyconnected, coupled or joined to the second component.

FIG. 1 is a diagram illustrating a wireless communication system towhich an embodiment of the present invention is applied.

The wireless communication system provides various communicationservices such as voice data, packet data, and the like.

Referring to FIG. 1, the wireless communication system may include aUser Equipment (UE) 10 (hereinafter referred to as a “UE”) and a basestation 20 (Evolved-Node-B; hereinafter referred to as an “eNodeB”). TheUE 10 and the eNodeB 20 may use a muting information generationtechnology and a channel state acquiring technology using thereof asdescribed below, and the muting information generation technology andthe channel state acquiring technology will be described below withreference to FIG. 2.

The UE 10 in the present disclosure may be a term including an MS(Mobile Station), a UT (User Terminal), an SS (Subscriber Station), awireless device and the like.

The eNodeB or a cell may refer to a fixed station where communicationwith the UE is performed, and may also be referred to as a Node-B, asector, a site, a BTS (Base Transceiver System), an access point, arelay node, and the like.

The eNodeB may be construed as an inclusive concept indicating a portionof an area or a function covered by a BSC (Base Station Controller) inCDMA, a radio network controller (RNC) in WCDMA, and the like. Further,the concept may include various coverage areas, such as a megacell, amacrocell, a microcell, a picocell, a femtocell, and a relay nodecommunication range.

In the present disclosure, uplink transmission and downlink transmissionin the eNodeB may be performed based on a Time Division Duplex (TDD)scheme that performs transmission based on different times, or based ona Frequency Division Duplex (FDD) scheme that performs transmissionbased on different frequencies.

An embodiment of the present invention is described for an example of awireless communication system, which may be applicable to resourceallocation in an asynchronous wireless communication scheme that evolvesthrough GSM, WCDMA, and HSPA, to LTE (Long Term Evolution) andLTE-advanced, and may be applicable to resource allocation in asynchronous wireless communication scheme that evolves to CDMA,CDMA-2000, and UMB. The present invention may not be limited orrestricted to a specific wireless communication scheme, and may includeall technical fields to which a technical idea of the present inventionis applicable.

The wireless communication system to which the embodiments of thepresent invention are applied may support an uplink and/or downlink HARQand may use a CQI (channel quality indicator) for link adaptation. Inaddition, multiple access systems for transmitting downlink and uplinkmay be different from each other. For example, a multiple access systemfor downlink may use OFDMA (Orthogonal Frequency Division MultipleAccess) and a multiple access system for the uplink may use SC-FDMA(Single Carrier-Frequency Division Multiple Access).

Meanwhile, in an example of a wireless communication system to which anembodiment of the present invention is applied, a radio or radio frameis configured by ten subframes and a subframe may include two slots.

A basic unit for data transmission is a unit of subframe, and downlinkor uplink scheduling is performed in a unit of subframe. One slot mayinclude a plurality of OFDM symbols in a time region.

For example, a subframe is configured by two time slots, and each timeslot may include seven or six OFDM symbols in a time region.

In this manner, a time-frequency region defined as 12 subcarriers(subcarriers or subcarriers) corresponding to one slot in a time regionor 180 KHz in a frequency region may be called a resource block (RB).

General structures of a subframe and a time slot of transmission dataapplicable to an embodiment of the present invention is described asfollows.

In 3GPP LTE or the like, time for transmitting a frame is divided by aTTI (Transmission Time Interval) with a duration time of 1.0 ms. Theterms, “TTI” and “sub-frame” may mean the same, and a frame is 10 mslong, and includes 10 TTIs.

As described above, a TTI is a basic transmission unit. One TTI includestwo time-slots of the same length and each time-slot has a duration timeof 0.5 ms. The time-slot includes 7 (or 6) long blocks (LBs) for asymbol. An LB is divided into cyclic prefixes (CPs). In sum, one TTI orsubframe may include 14 (or 12) LB symbols, but the present disclosureis not limited to such a frame, a subframe, or a time-slot structure.

Each TTI or subframe is divided into 14 (or 12) symbols (axes) in a timeregion. Each symbol (axis) may carry one symbol.

Further, 20 MHz of the whole bandwidth of the system may be divided orsplit into subcarriers in different frequencies, and an example thereofis configured to be divided into 12 succeeding subcarriers correspondingto 180 KHz.

For example, 10 MHz of a bandwidth in a slot may include 50 RBs in afrequency region.

Each grid space of a time-frequency region configured by each subcarrierin each symbol in a time region and each subcarrier in a frequencyregion may be called a resource element (hereinafter referred to as an“RE”). Each time-frequency region in the structure as described aboveconfigured by a pair of one subframe (1 TTI) in a time region and oneresource block (RB) corresponding to 12 subcarriers in a frequency axismay have 14×12=168 (or 12×12=144) REs.

Meanwhile, in an LTE communication system, various reference signals(RSs) are defined in downlink, such as a Cell-specific Reference Signal(CRS), a Multicast/Broadcast over Single Frequency Network ReferenceSignal (MBSFN-RS), and a UE-specific Reference Signal.

Among these, a CRS is a reference signal for a unicast transmission, notfor an MBSFN transmission. The CRS is to be included in all downlinkframes in cells that do not support a MBSFN transmission and to betransmitted. In addition, the CRS should be transmitted from one or moreof antenna ports 0 to 3.

In addition, one reference signal is transmitted to each downlinkantenna port, and an RE used for one CRS transmission in an antenna portin a slot may not be used for another antenna port in the same slot.

If CRSs are mapped to REs in different time-frequency regions for 4antenna ports, each of the REs to which CRSs for each antenna port areallocated has a cycle of 6 with respect to subcarriers, which is definedby the following equation.ν_(shift=N) _(ID) ^(cell) mod 6  [Equation 1]

Meanwhile, as described above, some next generation communicationtechnologies provide up to 8 antennas for downlink. Therefore, theexisting CRSs which are defined for four antennas are not sufficient fordetermining channel information at the time of downlink transmission.For this, a reference signal of a CSI-RS is newly defined so thatchannel state information with respect to up to 8 antennas can bedetermined.

In the CSI-RS currently discussed in LTE-A, one RE is allocated for eachantenna port per duty cycle in a time axis in an area of 12 subcarrierscorresponding to one resource block in a frequency axis with respect toeach cell.

That is, up to 8 REs are allocated and transmitted for 8 antenna portsin total. At this time, the duty cycle corresponds to multiples of 5 msof time configured by 5 subframes (that is, the duty cycle may be 5 ms,10 ms, or the like).

If the duty cycle is 5 ms, the CSI-RSs are transmitted to up to 2subframes out of 10 subframes in a radio frame which correspond to 10ms. Therefore, if a CSI-RS pattern for one subframe is defined, CSI-RSscan be allocated to the other subframes with a duty cycle.

In the present disclosure, the duty cycle for the CSI-RS transmission isdefined as a CSI-RS transmission duty cycle.

Meanwhile, a discussion has been made with respect to a communicationsystem using up to 8×8 multiple input multiple output (MIMO) antennas inboth transmission and reception terminals. Since a different CSI-RS isto be transmitted for each antenna port or layer, a transmitter is toallocate CSI-RSs for up to 8 antenna ports differently fromtime-frequency region to time-frequency region. Especially, CSI-RSs areto be allocated also differently from cell to cell in a multi-cellenvironment.

At this time, a basic definition of a CSI-RS has been determined andoverhead for each antenna port in one subframe are currently defined asdescribed above. However, a method for allocating and transmittingCSI-RSs for each antenna/base station (cell) has not been specificallydefined.

FIGS. 2 to 13 are diagrams illustrating representative examples formapping CSI-RSs to one subframe, which are CSI-RS patterns defined byframe structures (hereinafter referred to as “FS”) of subframes, normalor extended cyclic shifts (hereinafter referred to as “CP”), and thenumber (one of 2, 4, and 8) of antenna ports.

First, FIGS. 2 to 5 are CSI-RS patterns for a normal CP which arebasically (mandatorily) applied to all of FS1 (Frame Structure 1, FDD)and FS2 (Frame Structure 2, TDD (excluding special subframes)).

As illustrated in FIG. 2, in the case of a normal subframe, CSI-RSs areallocated to resources in one subframe reflecting already used locationsof CRS regions, control regions, and DM-RS (Demodulation ReferenceSignal) Rel-9/10 regions among 14 symbols in total so that the CSI-RSsare not overlapped with the CRS regions, the control regions, and theDM-RS (Demodulation Reference Signal) Rel-9/10 regions. In FIG. 2,unshaded REs are regions to which CSI-RSs can be allocated.

FIGS. 3 to 5 illustrate all possible CSI-RS patterns with respect to thenumber of antenna ports in a resource region as illustrated in FIG. 2.Each CSI-RS pattern is distinguished with alphabet subscripts.

As illustrated in FIG. 3, in the case of 8 antenna ports (antenna portnumbers 0 to 7), the CSI-RS patterns may be 5 in total from “a” to “e”patterns.

In FIG. 3 or the following figures, numerals are antenna port numbersand alphabet subscripts are identifiers indicating CSI-RS patterns ormuting patterns.

Meanwhile, when the number of CSI-RS antenna ports is 2 or 4, not 8,CSI-RS patterns are configured by a nested structure where the number ofCSI-RS antenna ports is 8.

That is, patterns when the number of CSI-RS antenna ports is 4 areconfigured by patterns divided from each specific pattern where thenumber of CSI-RS antenna ports is 8. Accordingly, the total number ofthe patterns is two times the number of the patterns where the number ofthe CSI-RS antenna ports is 8. Patterns when the number of CSI-RSantenna ports is 2 are also configured by patterns divided from eachspecific pattern where the number of CSI-RS antenna ports is 4.Accordingly, the total number of the patterns is two times the number ofthe patterns where the number of the CSI-RS antenna ports is 4.

For example, as illustrated in FIGS. 3 to 5, CSI-RS patterns basicallyapplied to a case of a normal CP in one subframe is 5 types (“a” to “e”illustrated in FIG. 3) when the number of CSI-RS antenna ports is 8, is10, which is two times thereof, (“a” to “j” illustrated in FIG. 4) whenthe number of CSI-RS antenna ports is 4, and becomes 20 (“a” to “t”illustrated in FIG. 5) when the number of CSI-RS antenna ports is 2.

FIGS. 6 to 9 illustrate CSI-RS patterns for extended CPs which aregenerally applied to all FS1 and FS2 (excluding special subframes).

As illustrated in FIG. 6, in the case of an extended CP, CSI-RSs areallocated to resources reflecting already used locations of CRS regions,control regions, and DM-RS Rel-9/10 regions among 12 symbols in totalused for downlink so that the CSI-RSs are not overlapped with the CRSregions, the control regions, and the DM-RS (Demodulation ReferenceSignal) Rel-9/10 regions. In FIG. 7, unshaded REs are regions to whichCSI-RSs can be allocated.

FIGS. 7 to 9 illustrate possible CSI-RS patterns in a resource region asillustrated in FIG. 6 according to the number of antenna ports. EachCSI-RS pattern is differentiated by an alphabet subscript.

As illustrated in FIG. 7, in the case of 8 antenna ports (antenna portnumbers 0 to 7), CSI-RS patterns may be 4 in total from “a” to “d”patterns.

In addition, in the case of 2 or 4 antenna ports, principles asillustrated in FIGS. 3 to 5 can be applied.

That is, as illustrated in FIGS. 7 to 9, CSI-RS patterns that arebasically applied with respect to an extended CP in one subframe are 4types when the number of CSI-RS antenna ports is 8 (“a” to “d” in FIG.7), are 8 types, which are two times thereof, (“a” to “h” illustrated inFIG. 4) when the number of CSI-RS antenna ports is 4, and becomes 16types (“a” to “p” illustrated in FIG. 5) when the number of CSI-RSantenna ports is 2.

FIGS. 10 to 13 illustrate examples of CSI-RS patterns applied to FS2 asadditional options. FIGS. 10 and 11 are cases of normal CPs, and FIGS.12 and 13 are cases of extended CPs.

FIG. 10 illustrates resource regions to which CSI-RSs can be allocatedto FS2 as an additional option. In the case of a normal subframe,CSI-RSs can be allocated to resources reflecting already used locationsof CRS regions, control regions, DM-RS Rel-9/10 regions, DM-RS(UE-specific RS) regions of Rel-8 among 14 symbols in total so that theCSI-RSs are not overlapped with the CRS regions, the control regions,and the DM-RS (Demodulation Reference Signal) Rel-9/10 regions. In FIG.10, unshaded REs are regions to which CSI-RSs can be allocated.

FIG. 11 illustrates possible CSI-RS patterns in the case where thenumber of antenna ports is 8 in a resource region as illustrated in FIG.10. The CSI-RS patterns may be 3 types in total from “a” to “c”patterns.

In addition, though it is not illustrated, if a resource region includes2 or 4 antenna ports, according to the principle as described above,CSI-RS patterns are 6 types, which are two times thereof, when thenumber of CSI-RS antenna ports is 4, and CSI-RS patterns may be 12 typeswhen the number of CSI-RS antenna ports is 2.

FIG. 12 illustrates resource regions to which CSI-RSs can be allocatedto FS2 as an additional option. In the case of a subframe for anextended CP, CSI-RSs can be allocated to resources reflecting alreadyused locations of CRS regions, control regions, and DM-RS Rel-9/10regions, among 12 symbols in total so that the CSI-RSs are notoverlapped with the CRS regions, the control regions, and the DM-RSRel-9/10 regions. In FIG. 10, unshaded REs are regions to which CSI-RSscan be allocated. In the case of a subframe for an extended CP, CSI-RSscan be allocated to resources reflecting already used locations of CRSregions, control regions, and DM-RS Rel-9/10 regions among 12 symbols intotal so that the CSI-RSs are not overlapped with the CRS regions, thecontrol regions, and the DM-RS (Demodulation Reference Signal) Rel-9/10regions. In FIG. 12, unshaded REs are regions to which CSI-RSs can beallocated.

FIG. 13 illustrates all possible CSI-RS patterns when the number ofantenna ports is 8 in a resource region as illustrated in FIG. 12. TheCSI-RS patterns may be 7 types in total from “a” to “g” patterns. Inaddition, though it is not illustrated, if a resource region includes 2or 4 antenna ports, according to the principle as described above,CSI-RS patterns are 14 types, which are two times thereof, when thenumber of CSI-RS antenna ports is 4, and CSI-RS patterns may be 28types, when the number of CSI-RS antenna ports is 2.

For the sake of easier description, in the present disclosure, a set ofa plurality of CSI-RS patterns defined by whether a CSI-RS is normal oradditional, whether a CP is normal or extended, and the number ofantenna ports (one of 2, 4, and 8) is defined as a CSI-RS pattern groupor a muting pattern group. A specific CSI-RS pattern which issubstantially adopted in the group is defined as a CSI-RS pattern or amuting pattern.

However, the terms are not limited thereto, and other expressions orterms may be used as long as they have the same or equivalent concept.

For example, when a CSI-RS pattern is generally applied to a normalsubframe and antenna ports are 8 (antenna port numbers 0 to 7) (like thecase of FIG. 3), each of the 5 CSI-RS patterns in total from “a” to “e”patterns may be a CSI-RS pattern group or a muting pattern group. Amongthem, according to the number of the CSI-RS antenna ports such as 2, 4,or 8, a pattern specified for actual CSI-RS allocation and muting may bedefined by a CSI-RS pattern or a muting pattern.

FIG. 14 illustrates a multicell environment such as a cooperativemultipoint Tx/Rx system (hereinafter referred to as ‘CoMP’).

The multicell environment to which the present invention can be appliedincludes CoMP, but the multicell environment is not limited thereto. Itshould be understood that the multicell environment includes all thecases where one user equipment should receive CSI-RSs from two or morecells or base stations.

In a CoMP wireless communication system, which is one of the multicellenvironments, a user equipment (UE) receives information from one ormore base stations or cells. In a communication system where acorresponding user is required to transmit and receive reference signalsnot only to a serving cell which mainly performs transmission andreception but also to a neighboring cell, CSI-RSs of the neighboringcell have weaker reception power than those of the serving cell.Therefore, it is difficult for the user to properly detect CSI-RSs fromthe neighboring cell if the serving cell and the neighboring cellsimultaneously transmit CSI-RSs from the same time/frequency source orthe serving cell transmits data and the neighboring cell transmitsCSI-RSs.

For example, in FIG. 14, 3 cells of Cell A, Cell B, and Cell C form aCoMP set, and a specific UE in Cell A which is a serving cell receivesnot only CSI-RSs from Cell A but also CSI-RSs from Cell B and Cell C tomeasure channel state information. At this point, each cell has one ofthe patterns defined in FIGS. 2 to 13 as a CSI-RS pattern.

For example, if each cell has 8 CSI-RS antenna ports with a generalCSI-RS pattern of a normal CP, each cell transmits CSI-RSs in one of the5 patterns as illustrated in FIG. 3. That is, for example, Cell A is afirst pattern of the 5 patterns, Cell B is a second pattern of the 5patterns, and, Cell C is a fourth pattern of the 5 patterns. Informationon the patterns may be implicitly determined based on Cell ID, or may beexplicitly determined by scheduling or signaling of an upper layer toeach base station.

Here, in view of Cell A which is a serving cell, Cell A transmitsCSI-RSs to an area corresponding to the first pattern which is a CSI-RSpattern with respect to Cell A among five patterns, and transmits DATAto the second, third, fourth, and fifth patterns which are CSI-RSpatterns with respect to the other cells. In view of a UE in Cell A, theUE performs decoding with a knowledge that CSI-RSs for Cell A istransmitted to the area corresponding to the first pattern amonginformation received from Cell A which is a base station, and the UEperforms decoding with a knowledge that data is transmitted to the areascorresponding to the other second, third, fourth, and fifth patterns.

However, in a multicell environment such as CoMP, it is necessary forthe resource region corresponding to the second pattern to receive notonly data but also CSI-RSs from Cell B. Even though CSI-RSs aretransmitted at a higher transmission power than data, CSI-RS informationfrom Cell B which is farther from the UE may experience more seriousintervention from data information from Cell A which is closer from theUE. Therefore, Cell A may perform muting, which implies zero powertransmission without transmitting data to a resource region to whichCell B transmits CSI-RS, so that the UE in Cell A receives CSI-RSinformation from Cell B without intervention.

In addition, in view of the UE in Cell A, the UE knows that not datafrom Cell A, but information muted with zero power is transmitted to aresource region to which Cell B transmits CSI-RSs, and that CSI-RS aretransmitted from Cell B, and the UE decodes the CSI-RS.

That is, if CSI-RS patterns are configured to each cell in considerationof a multicell environment such as CoMP, muting, which implies zeropower transmission without transmitting data, may be performed on a partwhere a CSI-RS is configured according to a CSI-RS pattern in theneighboring cell that configures a CoMP set in order to reduce theinfluence of the intervention by the neighboring cell.

As illustrated in FIG. 14, in view of Cell A which is a serving cell,information of which Cell A informs the UE in Cell A may be CSI-RSpatterns of the corresponding Cell A, the number of CSI-RS antennaports, a CSI-RS transmission cycle, and a transmission offset.

However, the UE in Cell A which is a serving cell does not know theinformation relating to CSI-RSs of neighboring cells in a multicellenvironment. In this circumstance, if muting is performed in order toreduce the influence of intervention by neighboring cells, the UE inCell A, which is a serving cell, does not know whether Cell A transmitsdata to a resource region which has CSI-RS patterns in the neighboringcell or performs muting with zero power. Therefore, there may be aproblem at the time of performing decoding.

In order to solve this problem, the present embodiment applies atechnology of transmitting, to a user equipment, information on whetheror not each cell performs muting on a CSI-RS resource region to havepossible CSI-RS patterns of the neighboring cells, that is, mutinginformation.

For this, the simplest way is to provide information on whether mutingis to be performed to all parts that are to have possible CSI-RSpatterns of neighboring cells or data is to be transmitted throughone-bit signaling without muting (which may be upper layer signalingthrough RRC or PDCCH signaling).

That is, for example, if each cell has 8 CSI-RS antenna ports configuredin a general CSI-RS pattern of a normal CP, each cell may be configuredby one of the five patterns illustrated in FIG. 3. If it is assumed thata serving cell is Cell A, Cell A informs each UE of information onwhether muting is performed on all regions to which CSI-RSs for all theother cells are to be transmitted except regions to which CSI-RSs forCell A is to be transmitted through one-bit signaling, or data is to betransmitted without muting.

However, when muting is performed on all areas, areas to which data isnot transmitted may be unnecessarily large in order to reduceintervention from neighboring cells in a multicell environment.Therefore, resources may be wasted. When data is transmitted withoutperforming muting on all areas, there may be a problem of interventionby neighboring cells. Therefore, it is effective not to perform mutingon all possible CSI-RS patterns but to perform muting on partialnecessary areas. A base station needs to signal information about wherethe partial areas are to a UE.

That is, the corresponding base station signals the portion, in whichmuting, which implies zero power transmission without transmitting data,is to be performed, among the parts for configuration of a CRS-RS ineach neighboring cell, to each UE. At this time, a muting region whichis signaled may be all or partial portions where all possible CSI-RSs ofneighboring cells are configured, and the CSI-RS pattern of theneighboring cells configuring a CoMP set is configured in considerationof CSI-RS patterns, the number of CSI-RS antenna ports of respectiveneighboring cells, a muting duty cycle (period or cycle) ontime/frequency or an offset.

In specific, a method for transmitting muting information according tothe present embodiment includes steps of receiving neighboring cellinformation including one or more of CSI-RS patterns, the number ofCSI-RS antenna ports, a CSI-RS transmission cycle, CSI-RS transmissionsubframe offset information; a step of determining a muting region whichis a time/frequency region that is overlapped with CSI-RSs of thecorresponding neighboring cell and requires muting, based on neighboringcell information; a step of generating muting information including afirst data field that indicates the muting region and indicates a mutingduty cycle and a muting offset of a muting subframe, and a second datafield that indicates one or more of a muting pattern group and aspecific muting pattern in the muting subframe; and a step oftransmitting the generated muting information to a user equipment.

The step of generating muting information may further include a firststep of generating a first data field determining a muting duty cycleand a muting offset and indicating the determined muting cycle andmuting offset; and a second step of generating a second data field thatindicates one or more of a muting pattern group and a specific mutingpattern in one muting subframe.

The performance method of the first step may be determined based on alocation of the muting subframe in which the muting is required and arelation between CSI-RS transmission cycles and CSI-RS transmissionoffset of the specific cell or the neighboring cell. This will bedescribed below in detail.

Therefore, the muting information according to the present embodimentmay have separate values per neighboring cells or a unified singlevalue, and includes a first data field indicating a muting duty cycleand a muting offset, and a second data field indicating one or more of amuting pattern group and a specific muting pattern in one mutingsubframe.

FIG. 15 illustrates a flow of a method of transmitting CSI-RS mutinginformation according to the present embodiment.

The method of transmitting CSI-RS muting information according to thepresent embodiment is performed in a serving cell or a serving basestation that currently provides service to the user equipment in amulticell environment, but the method is not limited thereto.

The method of transmitting CSI-RS muting information according to thepresent embodiment may include a step of receiving, from a neighboringcell, information including one or more of CSI-RS patterns, the numberof CSI-RS antenna ports, a CSI-RS transmission cycle, and CSI-RStransmission subframe offset information (S1505); a step of determininga muting region which is a time/frequency region that is overlapped withCSI-RSs of the corresponding neighboring cell and requires muting, basedon neighboring cell information (S1510); a step of generating mutinginformation including a first data field that indicates the mutingregion and indicates a muting duty cycle and a muting offset of a mutingsubframe, and a second data field that indicates one or more of a mutingpattern group and a specific muting pattern in one muting subframe(S1515); and a step of transmitting the generated muting information toa user equipment (S1520).

In addition, the method of transmitting CSI-RS information according tothe present embodiment may further include a step of performing resourceelement mapping including a muting process for performing zero powertransmission without transmitting data to the muting region inconsideration of the determined muting region at the time of resourceelement mapping to a resource region (PDSCH, Physical Downlink ResourceChannel) for data transmission and transmits this to the user equipment(S1525). The step S1525 may be configured after the step S1520 oftransmitting the muting information to the user equipment, or may beconfigured after the step S1510 of determining the muting region, or thestep S1515 of generating the muting information.

In step S1505, the corresponding base station receives neighboring cellinformation including information on one or more of CSI-RS patterns, thenumber of CSI-RS antenna ports, CSI-RS transmission subframe offset, anda CSI-RS transmission cycle in one subframe configured in eachneighboring base station from a neighboring base station as an object ofmuting. At this time, the neighboring base station (cell) as an objectof muting may be all neighboring base stations (cells) having differentCSI-RS patterns, may be some neighboring base stations (Cell B and CellC in FIG. 14) that form a CoMP set except a serving cell (Cell A in FIG.14) as illustrated in FIG. 14, or may be one or more neighboring basestations (cells) as objects of muting.

Step S1505 is information transmission between base stations (cells),and an example thereof may be information transmission through X2interface, but the step is not limited thereto.

The muting region means a region where zero power transmission withouttransmitting data is performed since there may be intervention on aregion to which CSI-RSs of a neighboring cell are allocated when aserving cell allocates a resource region (PDSCH) for data transmission,and the muting information means information used for designating theregion.

FIG. 16 is a flowchart illustrating a detailed configuration for stepsof generating muting information in an embodiment of the presentinvention.

The step of generating muting information in FIG. 15 (S1515) includes afirst step S1605 of generating a first data field for determining amuting duty cycle and a muting offset and indicating the muting dutycycle and the muting offset and a second step S1610 of generating asecond data field indicating one or more of a muting pattern group and aspecific muting pattern in one muting subframe.

A base station corresponding to a serving cell configures mutinginformation indicating a muting region where transmission with zeropower without transmitting data is performed with 2 steps in total. Thefirst step of the two may be performed at the very first time, but thefirst step may also be performed at the end after the second step isperformed. The information configured through the first and second stepsis signaled to the user equipment (UE), and the corresponding cellperforms muting, which implies zero power transmission withouttransmitting data, according to a muting pattern from the correspondingneighboring cell in a subframe corresponding to a muting offset percorresponding muting duty cycle based on the muting information.

At this time, information relating to muting which is transmitted orsignaled to the user equipment may be transmitted through an upper layersignaling such as RRC, or may be dynamically transmitted through PDCCH.

The user equipment in a serving cell performs decoding in considerationof a muting region (that is, a muted part where zero power transmissionwithout transmitting data is performed) which is known by signaledmuting information. If the UE does not know whether data is transmittedto the corresponding PDSCH region, or muting, which implies zero powertransmission without transmitting data, is performed (and if the UE doesnot know whether or not data is not transmitted to the time/frequencyresource region and CSI-RSs from a neighboring cell are transmitted),there may be an error or decrease in quality at the time of decoding.However, when decoding is performed in consideration of the mutinginformation described above, these problems are not generated.

Herein below, specific configurations of the first and second steps forconfiguring the muting information, that is, processes for configuringthe muting information, types of configured information, and the numberof bits are described in detail.

First Step

Hereinafter, each case of the first step of generating a first datafield for determining a muting duty cycle and a muting offset andindicating the muting duty cycle and the muting offset is described.

The first step is for specifying a subframe as an object of muting inconsideration of information relating to CSI-RSs of each correspondingneighboring cell as an object of muting. The information is configuredthrough a muting duty cycle and a muting offset, and a base stationperforms muting in a subframe expressed by the corresponding mutingoffset per muting duty cycle.

The information may be transmitted as one unit of information which isthe same for each corresponding neighboring cell as an object of muting(in this case, the muting information is the same for the neighboringcells as an object of all muting, so one unit of information istransmitted), or a plurality of units of information per correspondingneighboring cell as an object of all muting may be transmitted (in thiscase, the muting information may be different from neighboring cell toneighboring cell as an object of muting, so the number of transmissionsof information corresponds to the number of the neighboring cells as anobject of muting).

This first step can be divided into 5 cases according to a relation of amuting duty cycle and a muting offset with a CSI-RS transmission cycleand a CSI-RS transmission offset of a serving cell. The 5 cases will bedescribed in 1) to 5) below.

That is, the first step may be realized by differentiation in variousways according to a relation of a subframe which requires muting (thatis, a muting subframe) among CSI-RSs of a serving cell with a CSI-RStransmission cycle and a CSI-RS transmission offset of the serving cellor the neighboring cell in consideration of intervention with theneighboring cells.

Bit

1) A CASE WHERE A MUTING DUTY CYCLE AND A MUTING OFFSET ARE THE SAME ASA CSI-RS TRANSMISSION CYCLE AND A CSI-RS TRANSMISSION OFFSET OF THESERVING CELL (Base Station) (This is a case where the muting duty cycleor the muting offset is the same for all the neighboring cells as mutingobjects, and the information configured below is transmitted as one unitof information which is the same for all the neighboring cells as mutingobjects.)

In this case, the number of bits that configure a first data field maybe 0 bits.

In this case, a serving cell determines that a subframe transmittingCSI-RSs is a subframe as an object of muting.

For example, when a CSI-RS transmission cycle of a serving cell is 10ms, and a transmission offset is 3, CSI-RS are transmitted to a fourthsubframe (subframe number 3). The fourth subframe becomes a subframe asa muting object, so special information is not required for designatinga subframe to which CSI-RS of the neighboring cell are transmitted.

2) A CASE WHERE A MUTING OFFSET IS THE SAME AS A CSI-RS TRANSMISSIONOFFSET OF A SERVING CELL, AND A MUTING DUTY CYCLE IS A MULTIPLE OF ACSI-RS TRANSMISSION CYCLE OF THE SERVING CELL (this is a case where amuting duty cycle or a muting offset is the same for all neighboringcells as muting objects, and basically the information configured belowis transmitted as one unit of information which is the same for all theneighboring cells as muting objects. However, for performing muting in amore correct manner, a muting offset is the same for all the neighboringcells as muting objects, but the muting duty cycle may be different fromneighboring cell to neighboring cell. The information configured belowis configured and transmitted in a separate manner for eachcorresponding neighboring cell as muting objects.)

In this case, the method can be divided into two detailedconfigurations, and this is described by dividing the method intoMethods 2-1, 2-2, and 2-3.

2-1) Method 2-1

Muting is not performed on all CSI-RS configuration subframes of theneighboring cell, but some CSI-RS configuration subframes of theneighboring cell are muted in order to reduce regions to which datacannot be transmitted by being muted.

At this time, the number of the information bits configuring a firstdata field may be 2 bits, 4 bits, 8 bits, . . . , and 2^(M) bits (M is anatural number). Further, ┌log₂M┐ bits may be additionally required, but┌log₂M┐ bits may not be transmitted. Here, M is a natural number, and Mmay be determined so that 2^(M) is equal to or larger than the maximummultiple value of the muting duty cycle for a CSI-RS transmission rate.

For example, if the maximum multiple value is 16, M=4. In this case, afirst data field may be configured to be any one value of 2, 4, 8, and16 bits and additional ┌log₂M┐ bits may be required for indicating thenumber of the configuration bits.

Here, if M=4, a bitmap is formed with 0 or 1 for each bit amonginformation bits configured with 2 bits, 4 bits, 8 bits, or 16 bits, andeach bit corresponds to one CSI-RS transmission cycle of a serving cell.

That is, with respect to a subframe corresponding to a CSI-RStransmission offset in each CSI-RS transmission cycle, if the a bitvalue thereof is 0, muting may be performed, and if the bit valuethereof is 1, data may be transmitted (of course, it may be configuredto transmit data when the bit value is 0, and to perform muting when thebit value is 1).

In addition, depending on how many bits the number of the informationbits configuring a first data field is, signaling may be performed with┌log₂M┐ bits. If M=4, the number of bits additionally included forsignaling is 2 bits. When the bit values are “00”, “01”, “10”, and “11”,the configured information bit values are 2 bits, 4 bits, 8 bits, and 16bits, respectively.

In this case, depending on each bit value of the information bitsconfiguring a first data field, only when the bit value is 0, it isdetermined that a subframe corresponding to a CSI-RS transmission offsetin a CSI-RS transmission cycle of a serving cell is a subframe as anobject of muting.

For example, when a CSI-RS transmission cycle of a serving cell is 10 msand an offset is 3, CSI-RSs are transmitted to the fourth subframe(subframe number 3). At this time, when the configured number ofinformation bits is 4 bits and the bit value is “0101”, muting isperformed in first and third transmission cycles among four transmissioncycles forming 40 ms in total, and a fourth subframe in eachtransmission cycle becomes a subframe as an object of muting.

2-2) Method 2-2

In this case also, muting is not performed on all CSI-RS configurationsubframes of the neighboring cell, but some CSI-RS configurationsubframes of the neighboring cell are muted in order to reduce regionsto which data cannot be transmitted by being muted. At this point, thenumber of bits configuring a first data field may be┌log₂2·(2^(M)−1)┐_(bits.)

A specific cycle, which is a multiple of a CSI-RS transmission cycle ofa serving cell, and an offset in the specific cycle are newly defined,and muting is performed only for a CSI-RS transmission cycle of aserving cell corresponding to an offset in the cycle.

For example, when M=4, the specific cycle is determined by a valuecorresponding to 2 times, 4 times, 8 times, and 16 times of a CSI-RStransmission rate of a serving cell. Thirty types of specific cycles intotal, 2 types, 4 types, 8 types, and 16 types when the a CSI-RStransmission rate is 2 times, 4 times, 8 times, and 16 times, areconfigured, and the total number of bits is 5 bits.

For example, if the bit value of 5 bits is 0 to 1, 2 types of offsetswhen the specific cycle is 2 times of a CSI-RS transmission cycle of aserving cell are expressed. If the bit value is 2 to 5, 4 types ofoffsets when the specific cycle is 4 times of the CSI-RS transmissioncycle of the serving cell are expressed. If the bit value is 6 to 13, 8types of offsets when the specific cycle is 8 times of the CSI-RStransmission cycle of the serving cell are expressed. If the bit valueis 14 to 29, 16 types of offsets when the specific cycle is 16 times ofthe CSI-RS transmission cycle of the serving cell are expressed.

Muting is performed only on a CSI-RS transmission cycle corresponding toan offset in a specific cycle, and muting is not performed on theothers. That is, it is determined that a subframe corresponding to aCSI-RS transmission offset in a CSI-RS transmission period of theserving cell expressed by the specific cycle and the offset is asubframe as an object of muting.

For example, if a CSI-RS transmission cycle of a serving cell is 10 ms,and an offset is 3, CSI-RSs are transmitted to the fourth subframe(subframe number 3). At this point, if the configured number ofinformation bits is 5 bits, and the bit value is “01010” (a bit value is10, and this corresponds to a case where a specific cycle is 8 times andan offset is 5), muting is performed only in a fifth transmission cycleamong 8 transmission cycles in which a CSI-RS transmission cycle of aserving cell is 80 ms, which is 8 times of 10 ms. A fourth subframe inthe transmission cycle is a subframe as an object of muting.

2-3) Method 2-3

A muting offset is not transmitted since the muting offset is the sameas a CSI-RS transmission offset of a serving cell, and a muting dutycycle is a multiple of the CSI-RS transmission cycle of the servingcell, so only the muting duty cycle is transmitted in a separate manner.For example, in the cases where the muting duty cycles are 1 time, 2times, 4 times, 8 times, and 16 times of a CSI-RS transmission cycle,these 5 cases are configured and transmitted with 3 bits. (In the abovecase, the exemplary types of the multiple values are five, but theconfiguration and the number of the multiple values may vary. Forexample, 4 cases of 1 time, 2 times, 4 times, and 8 times are configuredwith 2 bits, or 8 types of multiple values larger than the above 5 typesof values are configured by each types, and transmitted with 3 bits.)For example, if the CSI-RS transmission cycle of the serving cell is 10ms and the offset is 3, CSI-RS are transmitted to a fourth subframe(subframe number 3). At this point, if the configured number ofinformation bits is 3 bits and the bit value is “010” (if it isconfigured that the bit value is 2 and 000 is one time, 001 is twotimes, 010 is 4 times, or the like, this means that 4 times of a cycleof the serving cell is a muting duty cycle), 40 ms which is a four timesof 10 ms, which is a CSI-RS transmission cycle of a serving cell, is amuting duty cycle, and a muting subframe offset is 3 which is the sameas the subframe offset of the serving cell.

3) A CASE WHERE A MUTING OFFSET IS THE SAME AS A CSI-RS TRANSMISSIONOFFSET OF A SERVING CELL (BASE STATION), BUT A MUTING DUTY CYCLE MAY BEDIFFERENT FROM A CSI-RS TRANSMISSION CYCLE OF THE SERVING CELL (BaseStation) (This is a case where a muting offset is the same for allneighboring cells as an object of muting, but the muting cycles may bedifferent. Basically, the information configured as below is transmittedto each corresponding neighboring cell as an object of all muting in aseparate manner. However, in order to reduce the total number of bitsfor muting signaling, the muting duty cycle and a muting offset may bethe same for all neighboring cells as muting objects, and theinformation configured as below may be transmitted as one item ofinformation which is the same for all neighboring cells as mutingobjects.)

In this case, the method may be divided into two detailedconfigurations, and this is described by dividing the method intoMethods 3-1 and 3-2.

3-1) Method 3-1

In this case, the number of information bits configuring a first datafield may be ‘2 bits or 3 bits to be determined according to the numberN of neighboring cells as an object of each muting×the number of kindsof muting duty cycle (the number of information bits may be 2 bits whenthe kinds of duty cycles are equal to or less than 4, or may be 3 bitswhen the kinds of duty cycles are more than 4 and equal to or less than8)’, and the muting duty cycle is determined according to the configuredinformation bit value.

Based on a value of a CSI-RS of a serving cell (base station) modulo amuting duty cycle, a muting offset is determined, so that a subframe asan object of muting is determined from a subframe corresponding to amuting offset in a muting duty cycle per corresponding neighboring cellas an object of each muting.

In addition, the configured information bits may be configured in aseparate manner with respect to each corresponding neighboring cell asan object of muting.

For example, when the number of information bits configured in aspecific cell as an object of muting is 2 bits, if the bit value is“00”, the muting duty cycle is configured to be 5 ms, if the bit valueis “01”, the muting duty cycle is configured to be 10 ms, if the bitvalue is “10”, the muting duty cycle is configured to be 20 ms, and ifthe bit value is “11”, the muting duty cycle is configured to be 40 ms.If a cycle which is 80 ms or more is configured, the number of bits maybe 3 bits. At this point, the configured bit value is “10”, and themuting duty cycle is 20 ms. In addition, if the CSI-RS transmissionoffset of the serving cell is 3, a fourth subframe (subframe number 3)for every 20 ms is a subframe as an object of muting.

3-2) Method 3-2

In this case, the number of information bits configuring a first datafield is ‘the number N of neighboring cells becoming targets of eachmuting×2 bits (or 4 bits, 8 bits, . . . , and 2^(M) bits)’, andselectively ‘N×┌log₂M┐ bits’ may be additionally included. However,‘N×┌log₂M┐ bits’ may not be transmitted.

For example, if M=4, a bitmap is formed with 0 or 1 for each bit amonginformation bits configured with 2 bits, 4 bits, 8 bits, or 16 bits.Accordingly, each bit corresponds to 5 ms (or 10 ms) which is a minimumvalue in a duty cycle. That is, with respect to a subframe correspondingto a value of a CSI-RS transmission offset of a serving cell (basestation) modulo 5 (or 10) per a cycle of 5 ms (or 10 ms), if the bitvalue is 0, muting is performed, and if the bit value is 1, data istransmitted (of course, adversely, it may be configured to perform datatransmission when the bit value is 0, and to perform muting when the bitvalue is 1).

In addition, with respect to how many bits the number of configuredinformation bits is, separate signaling may be performed with ┌log₂M┐bits. If M=4, the number of bits that can perform separate signaling is2 bits. If the bit value is “00”, the configured number of informationbits is 2 bits, and if the bit values are “01”, “10”, and “11”, thenumbers of information bits are 4 bits, 8 bits, and 16 bits,respectively. In this case, the information bit configuring a first datafield may be configured in a separate manner with respect to eachcorresponding neighboring cell as an object of muting.

With respect to each configured bit value of an information bit, onlywhen the bit value is 0, it is determined that a subframe correspondingto a value of a CSI-RS transmission offset of a serving cell (basestation) per muting duty cycle corresponding to 5 ms (or 10 ms) modulo 5(or 10) is a subframe as an object of muting.

For example, if the number of information bits configuring a specificcell as an object of muting is 4 bits and the bit value is “0101”,muting is performed only in first and third duty cycles among 4 mutingcycles forming 5 ms×4=20 ms in total. When a CSI-RS transmission offsetof a serving cell (base station) is 8 (a CSI-RS transmission cycle is 10ms), a fourth subframe (subframe number 3) corresponding to 3corresponding to a value of this value modulo 5 is a subframe as anobject of muting.

4) A CASE WHERE A MUTING DUTY CYCLE IS THE SAME AS A CSI-RS TRANSMISSIONCYCLE OF A SERVING CELL (BASE STATION), BUT A MUTING OFFSET MAY BEDIFFERENT FROM A CSI-RS TRANSMISSION OFFSET OF THE SERVING CELL (BaseStation) (This is a case where a muting duty cycle is the same for allneighboring cells as objects of muting, but a muting offset may bedifferent, and the information configured as below may be transmitted ina separate manner with respect to each corresponding neighboring cell asan object of all muting)

This is a case where the number of information bits configuring a firstdata field is “the number N of neighboring cells as objects of eachmuting×2 to 4 bits”.

It is determined that a cycle for transmitting CSI-RSs of a serving cell(base station) is a muting duty cycle, and a muting offset is determinedby a bit value transmitted in each muting duty cycle. For example, if amuting duty cycle is 5 ms, the other 4 subframes except a subframe towhich PSS/SSS is transmitted are expressed with 2 bit information, andmuting offset is determined from this value. When a muting duty cycle is10 ms, the other 8 subframes except a subframe to which PSS/SSS istransmitted are expressed with 3 bit information. When a muting dutycycle is 20 ms, the other 16 subframes except a subframe to whichPSS/SSS is transmitted are expressed with 4 bit information. A subframeas an object of muting is determined from subframes corresponding to amuting offset in a muting duty cycle to per corresponding neighboringcell as an object of each muting.

The configured information bit may be configured in a separate mannerwith respect to each corresponding neighboring cell as an object ofmuting.

For example, it is determined a fifth subframe, of which the number ofinformation bits configuring a specific cell as an object of muting is 3bits, and the value is “010” and which is the fourth subframe exceptPSS/SSS, is a muting offset. When a cycle for transmitting CSI-RSs of aserving cell (base station) is 10 ms, a fifth subframe (subframe number4) for every 10 ms is a subframe as an object of muting.

5) A CASE WHERE A MUTING DUTY CYCLE AND A MUTING OFFSET MAY BE DIFFERENTFROM A CSI-RS TRANSMISSION CYCLE AND A CSI-RS TRANSMISSION OFFSET OF ASERVING CELL (Base Station) (This is a case where a muting duty cycleand a muting offset may be different with respect to each correspondingneighboring cell as an object of all muting, and the informationconfigured as below is transmitted in a separate manner with respect toeach corresponding neighboring cell as an object for all muting.)

This case is a configuration in which the number of information bitsconfiguring a first data field is “the number N of neighboring cells asan object each muting×┌log₂4·(2^(M)−1)┐”.

In this configuration, according to the configured information bitvalue, a muting duty cycle and a muting offset are determined. Forexample, if M=3, with respect to 3 types of cycles such as 5 ms, 10 ms,and 20 ms, 4 types, 8 types, 16 types of subframe offsets except PSS/SSSare configured into 28 types of cases in total, and the total bit numberis 5 bits.

For example, if the bit value with 5 bits is 0 to 3, 4 types of subframeoffsets when the cycle is 5 ms are expressed. If the bit value is 4 to11, 8 types of subframe offsets when the cycle is 10 ms are expressed.If the bit value is 12 to 27, 16 types of subframe offsets when thecycle is 20 ms are expressed. If M=4, with respect to four types ofcycles such as 5 ms, 10 ms, 20 ms, and 40 ms, 4 types, 8 types, 16types, and 32 types of subframe offsets except PSS/SSS are configuredinto 60 types of cases in total, and the total bit number is 6 bits.

For example, if the bit value with 6 bits is 0 to 3, 4 types of subframeoffsets when the cycle is 5 ms are expressed. If the bit value is 4 to11, 8 types of subframe offsets when the cycle is 10 ms are expressed.If the bit value is 12 to 27, 16 types of subframe offsets when thecycle is 20 ms are expressed. If the bit value is 28 to 59, 32 types ofsubframe offsets when the cycle is 40 ms are expressed. A subframe as anobject of muting is determined from a subframe corresponding to a mutingoffset in a muting duty cycle per corresponding neighboring cell as anobject of each muting.

In addition, the configured information bit may be configured in aseparate manner with respect to each corresponding neighboring cell asan object of muting.

For example, if the number of information bits configuring a specificcell is 5 bits, and the bit value is “01101” (the bit value is 13), themuting duty cycle is 20 ms, and the muting offset is 1. (when the bitvalue is 12 to 27, 16 types of the subframe offsets when the cycle is 20ms are expressed, that is, when the bit value is 12, an offset is 0, andwhen the bit value is 13, an offset is 1) Therefore, with respect to acorresponding neighboring cell, a second subframe (subframe number 2,and subframe number 0 indicates a subframe to which PSS/SSS is mapped)except PSS/SSS for every 20 ms is a subframe as an object of muting.

The explanations above are provided to describe examples of types forconfiguring a first data field among muting information of FIG. 15. Amethod for configuring a muting duty cycle or a muting offset indicatedby the first data field is not limited thereto.

In addition, each method described above is not applied by separatelydetermining on a case by case method, but one is selected and appliedaccording to a system configuration for CSI-RSs and a standardizedmethod. Each case may include another case (for example, the fifthmethod among the above methods may be regarded as a generalized caseincluding the other methods).

In the method above, an offset may be defined with respect to allsubframes in one radio frame without excluding a subframe to whichPSS/SSS is included, and in this case, the configured number of bits maybe increased a little bit. For example, in the above example, if M=5,except a subframe to which PSS/SSS is included, 124 types of cases intotal is configured with 7 bits. However, in the same manner, for 5types of cycles such as 5 ms, 10 ms, 20 ms, 40 ms, and 80 ms, withrespect to all subframes in the cycles, 5 types, 10 types, 20 types, 40types, and 80 types of subframes may be configured into 155 types ofcases in total, and the total bit number is 8 bits.

Second Step According to Embodiment Illustrated in FIG. 16

Herein below, a description is made of each case in a second step ofgenerating a second data field that determines a muting pattern group inone subframe or a direct specific muting pattern and indicates themuting pattern group or the specific muting pattern.

The second step may be divided into two types: Type 2-1 of configuring asecond data field so that information of a specific muting pattern isdirectly indicated without information of a muting pattern group andType 2-2 of configuring a second data field so that only a mutingpattern group is indicated. Type 2-1 that indicates a specific mutingpattern may only be subdivided into one of Types A, B, and C.

However, the second step is not limited to this division method, but mayinclude all methods of configuring a second data field so that a mutingregion in a muting subframe is indicated and one or more of a mutingpattern group and a specific muting pattern is indicated.

1) Type 2-1: Configuring a Second Data Field so that Only a MutingPattern is Indicated

In a general determination of a muting pattern group, when antenna portsare 2 or 4, the determination is performed like antenna ports are 8.Therefore, the muted region becomes larger. That is, a muted REincreases, but overhead for configuring muting information and signalingdecreases.

As described above, in Type 2-1, when a muting pattern is directlydetermined, a muting pattern is determined without determining a mutingpattern group.

The muting pattern group is a pattern group that is configured with 8REs like the case of 8 CSI-RS antenna ports in a CSI-RS pattern.

As to CSI-RSs which are basically applied to both of FS1 (FDD) and FS2(TDD) and is a normal CP, when the number of CSI-RS antenna ports in onesubframe is 8 as illustrated in FIG. 3, 5 CSI-RS patterns in total aredefined, so a muting pattern group is one of five types. With respect toan extended CP, when one subframe has 8 CSI-RS antenna ports asillustrated in FIG. 7, 4 CSI-RS patterns in total are defined, so amuting pattern is one of four types.

As illustrated in FIGS. 11 and 13, as to a CSI-RS applied as anadditional option in FS2 (TDD), with respect to a normal CP, if onesubframe has 8 CSI-RS antenna ports, 3 CSI-RS patterns in total aredefined, so a muting pattern group is one of 3 types. With respect to anextended CP, when one subframe has 8 CSI-RS antenna ports, 7 CSI-RSpatterns in total are defined, so a muting pattern is one of 7 types.

In this circumstance, three detailed Types A to C for realizing Type 2-1are described in detail.

A. Method 1 of Directly Indicating a Muting Pattern: Configuration isMade with 5 to 6 Bits Per Neighboring Cell as an Object of Each Muting

In Type A of Type 2-1, a figure of information bit configuring a seconddata field may be 5 bits or 6 bits for indicating each of mutingpattern×the number N of neighboring cells as objects of muting.

More specifically, as to CSI-RSs which are basically applied to both ofFS1 (FDD) and FS2 (TDD) and are in the case of a normal CP, when thenumber of CSI-RS antenna ports in one subframe is 8 as illustrated inFIG. 3, 5 CSI-RS patterns in total are defined, so a total number oftypes of muting patterns is 5 when antenna ports are 8, 10 when antennaports are 4, and 20 when antenna ports are 2. Therefore, a second datafield can be configured to indicate 35 types of muting patterns in totalwith 6 bits.

For example, with respect to 0 to 63 of the bit value when expression ismade with 6 bits, when the bit value is 0 to 4, 5 types of mutingpatterns when antenna ports are 8 are expressed, when the bit value is 5to 14, 10 types of muting patterns when antenna ports are 4 areexpressed, when the bit value is 15 to 34, 20 types of muting patternswhen antenna ports are 2 are expressed, and the rest of the bit valuesof 35 to 63 are reserved.

In addition, as to CSI-RSs which are basically applied to both of FS1(FDD) and FS2 (TDD) and are in the case of an extended CP, when thenumber of CSI-RS antenna ports in one subframe is 8 as illustrated inFIG. 7, 4 CSI-RS patterns in total are defined, so a total number oftypes of muting patterns is 4 when antenna ports are 8, 8 when antennaports are 4, and 16 when antenna ports are 2. Therefore, a second datafield can be configured to indicate 28 types of muting patterns in totalwith 5 bits. For example, with respect to 0 to 31 of the bit value whenexpression is made with 5 bits, when the bit value is 0 to 3, 4 types ofmuting patterns when antenna ports are 8 are expressed, when the bitvalue is 4 to 11, 8 types of muting patterns when antenna ports are 4are expressed, when the bit value is 12 to 27, 16 types of mutingpatterns when antenna ports are 2 are expressed, and the rest of the bitvalues of 28 to 31 are reserved.

As illustrated in FIGS. 11 and 13, as to a CSI-RS applied as anadditional option in FS2 (TDD), in the case of a normal CP, if onesubframe has 8 CSI-RS antenna ports, 3 CSI-RS patterns in total aredefined, so a total number of types of the muting patterns is 3 whenantenna ports are 8, 6 when antenna ports are 4, and 12 when antennaports are 2. Therefore, in a manner as described above, a second datafield can be configured so that 19 types of muting patterns in total areindicated with 5 bits.

As to CSI-RSs applied as an additional option in FS2 (TDD), in the caseof an extended CP, if one subframe has 8 CSI-RS antenna ports, 7 CSI-RSpatterns in total are defined, so a total number of types of the mutingpatterns is 7 when antenna ports are 8, 14 when antenna ports are 4, and28 when antenna ports are 2. Therefore, in a manner as described above,a second data field can be configured so that 49 types of mutingpatterns in total are indicated with 6 bits. Such a second data fieldmay be configured differently from neighboring cell to neighboring cellas an object of muting.

In addition, in the above, muting information is configured andtransmitted in a manner dividing into a case to be basically (generally)applied to FS1 and FS2 and a case to be optionally applied only to FS2.However, for convenience, the two cases may be combined and mutinginformation is configured and transmitted at the same time. For example,in the case of a normal CP, 35 types of cases to be basically(generally) applied to FS1 and FS2 and 21 types of cases to beoptionally applied only to FS2 are combined, and the 56 types areconfigured and transmitted with 6 bits. In this case, in FS2, asdescribed above, 56 types are configured with 6 bits, but only thepatterns to be basically (generally) applied exist in FS1. Therefore, inthis case, only 35 types are configured with 6 bits. In order to applythe same system to FS1 and FS2, FS1 may have muting informationconfigured with 6 bits in consideration of the 56 types.

In the case of an extended CP, patterns for cases to be optionallyapplied to FS2 already include patterns for cases to be basically(generally) applied to FS1 and FS2. Therefore, in the case ofconfiguration as described above, both of FS1 and FS2 may have themuting information configured 6 bits in consideration of 49 types ofcases.

B. Method 2 of Directly Indicating a Muting Pattern: Configuration isMade with 5 Bits Per Neighboring Cell as an Object of Each Muting

In Type B of Type 2-1, a figure of information bit configuring a seconddata field may be 5 bits×the number N of neighboring cells as objects ofmuting.

More specifically, as to CSI-RS for a normal CP which are basicallyapplied to both of FS1 (FDD) and FS2 (TDD), when the number of CSI-RSantenna ports in one subframe is 8 as illustrated in FIG. 3, 5 CSI-RSpatterns in total are defined, so a total number of types of mutingpatterns is 5 when antenna ports are 8, 10 when antenna ports are 4, and20 when antenna ports are 2. Therefore, 35 types of muting patterns intotal are defined. However, CSI-RSs of a neighboring cell as an objectof muting are not transmitted according to a pattern which at leastCSI-RSs transmitted by a serving cell include or in which CSI-RSs areincluded. Therefore, considering this, a muting pattern of a neighboringcell substantially as an object of muting can be defined.

For example, when a serving cell transmits a CSI-RS with 8 antennaports, the CSI-RS pattern for the 8 antenna ports may not be a CSI-RSpattern of a neighboring cell as an object of muting. Therefore, 7 typesthat the CSI-RS pattern of the serving cell includes among the total 35types (a pattern which the CSI-RS pattern of the corresponding servingcell is 1 type of pattern when antenna ports are 8, 2 types of patternswhen antenna ports are 4, 4 types of patterns when antenna ports are 2,and a total number of patterns by adding this is 7) may not be a CSI-RSpattern of a neighboring cell as an object of muting. The second datafield may be configured so that the rest of 28 types of muting patternsare indicated with 5 bits.

In addition, when a serving cell transmits a CSI-RS with 4 antennaports, the CSI-RS pattern for the 4 antenna ports may not be a CSI-RSpattern of a neighboring cell as an object of muting. Therefore, amongthe total 35 types, 4 types which the CSI-RS pattern of the serving cellincludes or in which the CSI-RS pattern is included (Patterns which theCSI-RS pattern of the serving cell with 4 antenna ports includes are 1pattern in the case of 4 antenna ports and 2 patterns in the case of 2antenna ports. In addition, a pattern in which the CSI-RS pattern of thecorresponding serving cell is included when the antenna ports are 4 is 1pattern including the same among patterns having 8 antenna ports.Therefore, a total number of types of patterns adding the same is 4.)may not be CSI-RS patterns of a neighboring cell as an object of muting,and a second data field may be configured so that the rest of 31 typesof muting patterns are indicated in a manner divided by 5 bits.

In addition, when the serving cell transmits a CSI-RS with 2 antennaports, the CSI-RS pattern for the two antenna ports may not be CSI-RSpatterns of a neighboring cell as an object of muting. Therefore, amongthe total 35 types, 3 types which the CSI-RS pattern of the serving cellinclude (Patterns which the CSI-RS pattern of the serving cell with 2antenna ports includes are 1 pattern in case of 2 antenna ports. Inaddition, a pattern in which the CSI-RS pattern of the correspondingserving cell with 2 antenna ports is included is 1 pattern including thesame among patterns having 8 antenna ports and 1 pattern including thesame among patterns having 4 antenna ports. Therefore, a total number oftypes of patterns adding the same is 3.) may not be CSI-RS patterns of aneighboring cell as an object of muting, and a second data field may beconfigured so that the rest of 32 types of muting patterns are indicatedin a manner divided by 5 bits.

In addition, as to CSI-RSs for an extended CP which are basicallyapplied to both of FS1 (FDD) and FS2 (TDD), when the number of CSI-RSantenna ports in one subframe is 8 as illustrated in FIG. 7, 4 CSI-RSpatterns in total are defined. At this point, in a manner as describedabove, when the serving cell transmits CSI-RSs with 8 antenna ports, asecond data field may be configured so that 21 types except 7 typesamong the total 28 types when the serving cell transmits CSI-RSs with 8antenna ports, 24 types except 4 types among the total 28 types when theserving cell transmits CSI-RSs with 4 antenna ports, and 25 types except3 types among the total 28 types when the serving cell transmits CSI-RSswith 2 antenna ports are indicated in a manner divided by 5 bits, butlike Type A described above, information of the total 28 types may beconfigured with 5 bits.

In the configuration, a case of a CSI-RS configuration applied as anadditional option of FIGS. 10 to 13 may be excluded.

The configured second data field is respectively configured perneighboring cell as an object of muting.

C. Method 3 of Directly Indicating a Muting Pattern: Configuration isMade with a Bitmap of 12 to 28

In Type C of Type 2-1, a figure of information bit configuring a seconddata field may be one bit value of “12 to 28 bits in total”.

The configuration of a second data field in each case is described asfollows.

As to CSI-RSs for a normal CP which are basically applied to both of FS1(FDD) and FS2 (TDD), when the number of CSI-RS antenna ports in onesubframe is 8 as illustrated in FIG. 3, 5 CSI-RS patterns in total aredefined, so 20 types of CSI-RS patterns are present in the case of 2antenna ports.

If this is configured by a bitmap with 20 bits, information relating toREs to be muted substantially in one subframe regardless of the numberof neighboring cells as objects of muting can be configured.

That is, with respect to each of total 20 patterns in the case of 2antenna ports configured by 2 REs, when the bitmap information is 0,muting is performed and when the bitmap information is 1, data istransmitted (otherwise, data is transmitted when the bitmap informationis 0, and muting is performed when the bitmap information is 1). If thenumber of CSI-RS antenna ports of a neighboring cell as an object ofmuting is 8, the case where the number of CSI-RS antenna ports asobjects of muting is 4 includes 4 cases in which the number of CSI-RSantenna ports is 2, so the bitmap values for the 4 cases are set to be0. Further, the case where the number of CSI-RS antenna ports as objectsof muting is 4 includes two cases in which the number of CSI-RS antennaports is 2. Therefore, the information may be configured by putting bothof the bitmap values for the two cases to be 0.

As to CSI-RSs for an extended CP which are basically applied to both ofFS1 (FDD) and FS2 (TDD), when the number of CSI-RS antenna ports in onesubframe is 8 as illustrated in FIG. 7, 4 CSI-RS patterns in total aredefined. At this point, in a manner as described above, the number oftypes of patterns for transmitting CSI-RSs with 2 antenna ports is 16,so this can be configured with bitmap information with 16 bits in amanner described above.

As illustrated in FIG. 11, as to CSI-RSs applied as an additional optionin FS2 (TDD), in the case of a normal CP, 3 types of CSI-RS patterns intotal are defined when the number of CSI-RS antenna ports in onesubframe is 8. At this time, the number of types of patterns fortransmitting CSI-RSs with 2 antenna ports is 12 in total. Therefore, ina manner as described above, this can be configured by bitmapinformation with 12 bits.

As illustrated in FIG. 13, as to CSI-RSs applied as an additional optionin FS2 (TDD), in the case of an extended CP, 7 types of CSI-RS patternsin total are defined when the number of CSI-RS antenna ports in onesubframe is 8. At this time, the number of types of patterns fortransmitting CSI-RSs with 2 antenna ports is 28 in total. Therefore, ina manner as described above, this can be configured by bitmapinformation with 28 bits.

In addition, in the above, muting information is configured andtransmitted in a manner dividing into a case to be basically (generally)applied to FS1 and FS2 and a case to be optionally applied only to FS2.However, for convenience, the two cases may be combined and mutinginformation is configured and transmitted at the same time. That is, inthe case of a normal CP, 20 types of cases to be basically (generally)applied to FS1 and FS2 and 12 types of cases to be optionally appliedonly to FS2 are combined, and the 32 types are configured andtransmitted by a bitmap with 32 bits. In this case, in FS2, as describedabove, 32 types are configured with 32 bits, but only the patterns to bebasically (generally) applied are present in FS1. Therefore, in thiscase, only 20 types are configured with 20 bits. In order to apply thesame system to FS1 and FS2, FS1 may have muting information configuredby a bitmap with 32 bits in consideration of the 32 types.

In the case of an extended CP, patterns for cases to be optionallyapplied to FS2 already include patterns for cases to be basically(generally) applied to FS1 and FS2. Therefore, in the case ofconfiguration as described above, both of FS1 and FS2 may have themuting information configured 28 bits in consideration of 28 types ofcases.

2) Type 2-2: Configuring a Second Data Field so that Only a MutingPattern Group is indicated

In Type 2-2 of configuring a second data field so that only a mutingpattern group is indicated, the second data field is configured with “3to 7 bits in total” (5 bits when it is basically applied to both of FS1(FDD) and FS2 (TDD) and is in the case of a normal CP).

Type 2-2 like this is not a method of muting only specific mutingpatterns in a muting pattern group according to the number of antennaports, but a method of muting all REs in the determined muting patterngroup.

The configuration of a second data field in each case is described asfollows.

As to CSI-RSs for a normal CP which are basically applied to both of FS1(FDD) and FS2 (TDD), when the number of CSI-RS antenna ports in onesubframe is 8 as illustrated in FIG. 3, 5 CSI-RS patterns in total aredefined. At this point, the number of patterns for transmitting CSI-RSswith 8 antenna ports is 5 in total. Therefore, a second data field maybe configured by bitmap information with 5 bits, and informationrelating to REs to be muted substantially in one subframe regardless ofthe number of neighboring cells as objects of muting can be configured.That is, each of total 5 patterns in the case of 8 antenna portsconfigured by 8 REs is configured by a bitmap with 5 bits, when thebitmap information is 0, muting is performed and when the bitmapinformation is 1, data is transmitted (otherwise, data is transmittedwhen the bitmap information is 0, and muting is performed when thebitmap information is 1).

In this manner, if a muting region is determined by a muting patterngroup, when each neighboring cell as an object of muting transmitsCSI-RSs with 2 or 4 antenna ports, muting is performed like the case ofantenna ports. Therefore, substantially more regions become regions asobjects of muting.

That is, since muted RE regions become large, there is a problem ofdecreasing regions to which data can be transmitted. However, there isan advantage of reducing overhead for configuring and signaling mutinginformation.

As to CSI-RSs for an extended CP which are basically applied to both ofFS1 (FDD) and FS2 (TDD), when the number of CSI-RS antenna ports in onesubframe is 8 as illustrated in FIG. 7, 4 CSI-RS patterns in total aredefined. At this point, the number of types of patterns for transmittingCSI-RSs with 8 antenna ports is 4, so a second data field can beconfigured with bitmap information with 4 bits in a manner describedabove.

As illustrated in FIG. 11, as to CSI-RSs for a normal CP which areapplied as an additional option in FS2 (TDD), 3 types of CSI-RS patternsin total are defined when the number of CSI-RS antenna ports in onesubframe is 8. At this time, the number of types of patterns fortransmitting CSI-RSs with 8 antenna ports is 3 in total. Therefore, in amanner as described above, a second data field can be configured bybitmap information with 3 bits.

As illustrated in FIG. 13, as to CSI-RSs for an extended CP applied asan additional option in FS2 (TDD), 7 types of CSI-RS patterns in totalare defined when the number of CSI-RS antenna ports in one subframe is8. At this time, the number of types of patterns for transmittingCSI-RSs with 8 antenna ports is 7 in total. Therefore, in a manner asdescribed above, a second data field can be configured by bitmapinformation with 7 bits.

In the above, a method of muting all REs in the determined mutingpattern group, not a method of muting only specific patterns in a mutingpattern group, is applied. At this point, a muting pattern group as areference is based on 8 antenna ports, but it may be based on 4 CSI-RSantenna ports.

The muting information generated as above may be transmitted by an upperlayer signaling such as RRC, may be dynamically transmitted by PDCCH inL1 layer, or may be signaled through MAC in L2 layer.

One or more of the cases described above may be selectively adoptedaccording to the specification of a communication system to which thepresent embodiment is applied for determining a muting region andgenerating muting information according to the present embodiment.

For example, depending on the type of the communication system, one ormore of various types for configuring first and second steps arecombined to configure the present invention.

In other words, the present invention may be configured not by adoptingall detailed types in the first and second steps described above, but bycombining one or more of various types configuring the first and secondsteps according to a specification of a communication system, aconfiguration of a CSI-RS, a CSI-RS pattern, the number of CSI-RSantenna ports, a CSI-RS transmission cycle, a CSI-RS transmissionsubframe offset, or the like.

FIG. 17 is a flowchart illustrating a method of acquiring channelinformation in a user equipment using muting information according tothe present embodiment.

A method for acquiring channel information according to the presentembodiment is to acquire channel information by receiving a CSI-RSsignal from two or more cells (base station). Generally, the method isperformed at a user equipment or at a UE, but the method is not limitedthereto.

A method for acquiring channel state includes a step of receiving mutinginformation including a first data field that indicates a muting dutycycle and a muting offset from a serving cell among two or more cellsand a second data field that indicates one or more of a muting patterngroup in one muting subframe and a specific muting pattern (S1705), astep of receiving CSI-RSs in consideration of muting (S1710); a step ofidentifying a muting region in a resource region for data transmissionin the serving cell by using the muting information and identifying aCSI-RS transmission region of a neighboring cell corresponding thereto(S1715); and a step of acquiring a channel state by decoding andestimating CSI-RSs of the serving cell and the neighboring cell inconsideration of the muting region (S1720).

In Step S1710, receiving CSI-RSs in consideration of muting meansreceiving CSI-RSs of a neighboring cell transmitted from a resourceregion of a neighboring cell corresponding to a partial region muted bythe muting information among a resource region (PDSCH) for transmittingCSI-RSs of the serving cell and the data of the serving cell.

The muting information received from the serving cell in Step S1705 isinformation indicating a region which is overlapped with CSI-RSs of theneighboring cell and to which data is not transmitted. The mutinginformation may be configured by the first and second data fielddescribed in relation to FIGS. 2 to 16.

Steps S1705 and S1710 described above may be configured with itssequence changed, or realized with the steps combined into one.

A CSI-RS signal received from the serving cell and the neighboring cellis a reference signal (a CSI-RS of the serving cell) already generatedin a region allocated in the serving cell for transmitting a CSI-RS or areference signal (a CSI-RS of the neighboring cell) generated in theresource region of the neighboring cells corresponding to a region towhich muting which implies non-transmission of data or zero powertransmission in a resource region (PDSCH) for transmitting data of theserving cell to match with the muting information as described above isapplied.

The process of identifying a muting region in Step S1715 may include astep of confirming a subframe in which a muting region is present byidentifying a muting duty cycle and a muting offset using a first datafield value of the received muting information; a step of determining amuting pattern group or a specific muting pattern in the muting subframeusing a second data field value; and a step of determining a mutingregion using the determined muting pattern group or the determinedspecific muting pattern, but the process is not limited thereto.

In Step S1720 of acquiring a channel state of the serving cell and theneighboring cell in consideration of a muting region, decoding isperformed in a manner of not considering REs which are muting regions atthe time of decoding when the user equipment decodes data received fromthe serving cell, a reference signal is decoded by decoding CSI-RSs ofthe neighboring cell which are received from a region corresponding tothe muted resource region and CSI-RSs of the serving cell which arereceived in advance, and then a channel state is measured and acquiredfrom them. According to this, the efficiency for decoding CSI-RSs may beimproved, and a CSI-RS of each cell can be correctly decoded byeliminating intervention from a CSI-RS of the neighboring cell.Therefore, correct channel estimation becomes possible.

FIG. 18 is a block diagram illustrating a configuration of a CSI-RSmuting information transmission apparatus according to the presentembodiment.

It is general that the CSI-RS muting information transmission apparatusaccording to the present embodiment is realized in the serving cell ofthe multicell environment or the serving base station, or in associationwith the multicell environment or the serving base station. The CSI-RSmuting information transmission apparatus is not limited thereto.

The CSI-RS muting information transmission apparatus according to thepresent embodiment may include a neighboring cell information receiver1810 that receives neighboring cell information including one or more ofa CSI-RS pattern, the number of CSI-RS antenna ports, a CSI-RStransmission cycle (Duty Cycle), and CSI-RS transmission subframe offsetinformation from one or more neighboring cells in a multicellenvironment; a muting region determining unit 1820 that determines amuting region which is a time/frequency resource region that overlapswith CSI-RSs of the corresponding neighboring cell in a resource spacethereof and therefore requires muting based on the neighboring cellinformation; a muting information generating unit 1830 that generatesmuting information including a first data field which indicates themuting region and indicates a muting duty cycle and a muting offset anda second data field which indicates one or more of a muting patterngroup and a specific muting pattern in one muting subframe; and a mutinginformation transmitter 1840 that transmits the generated mutinginformation to a user equipment (UE) that receives a CSI-RS.

The neighboring cell information receiver 1810 performs a function ofreceiving one or more units of information among CSI-RS patterns of eachneighboring cell, the number of CSI-RS antenna ports, a CSI-RStransmission cycle, and CSI-RS transmission subframe offset informationfrom neighboring cells (Cell B and Cell C in FIG. 14) which is totransmit CSI-RSs thereof to a specific user equipment in a multicellenvironment such as CoMP.

The muting region determining unit 1820 performs a function ofdetermining a muting region which is a time/frequency region thatoverlaps with CSI-RSs of the corresponding neighboring cell in aresource space thereof and therefore requires muting for transmittingdata of a serving cell based on the neighboring cell informationreceived from the neighboring cell.

The muting information generating unit 1830 generates muting informationthat indicates a muting region determined by a muting region determiningunit. In detail, as described in relation to FIGS. 2 to 16, a first datafield which indicates a muting duty cycle and a muting offset and asecond data field which indicates one or more of a muting pattern groupand a specific muting pattern in one muting subframe are generated andcombined to generate final muting information.

Such first and second data fields can be determined by types ofcombining one or more of various types in the first and second steps asdescribed in relation to FIG. 16. To avoid an overlapped description, adetailed description is omitted.

As an example of the muting information, it is assumed that acommunication system to which the present embodiment is applied hasconditions as follows.

1) Condition of the first step: The muting offset is identical to CSI-RStransmission offset of the serving cell (base station) (It is assumedthat the offset is 3), the muting duty cycle is a multiple of the CSI-RStransmission cycle of the serving cell (base station), M=4, andsignaling is separately performed by ┌log₂M┐=2 bits with respect howmany bits the number of information bits configuring the first datafield is (as a result, this corresponds to Type 2-1 in the first stepdescribed above, 6 bits in total)

2) Condition of the second step: This is a case where it is assumed thata second data field is configured so that a specific muting pattern isdirectly indicated, the second data field is basically applied to bothof FS1 (FDD) and FS2 (TDD) and is in the case of a normal CP, the numberof CSI-RS antenna ports is 8, and total 35 types of patterns (5 typesfor 8 antennas, 10 types for 4 antennas, and 20 types for 2 antennas)are indicated with 6 bits (As a result, this corresponds to Type A inType 2-1 of 2 steps described above; it is assumed that there are 6 bitsin total, Pattern b is a muting pattern in the case of 8 antennas, andthis is expressed with “000001”)

In this circumstance, muting information includes a bit value of a firstdata field with 6 bits and a bit value of a second data field with 6bits. This is configured as illustrated in FIG. 19.

That is, FIG. 19 illustrates an example of data format of mutinginformation according to the present invention.

If it is assumed that the first and second conditions described above,the muting information 1900 according to the present embodiment includesa first data field region 1910 configured with 6 bits of “101010” and asecond data field 1920 configured with 6 bits of “000001”.

If the meaning of each data field value is described in detail, a fieldvalue of the first data field region 1910 configured with 6 bits of“101010” may be subdivided into 2 bit value (log₂M=2) of “10” indicatinga configuration bit value (M=4) and a region with 4 bits of “1010”indicating an actual muting duty cycle and a muting offset.

As a result, the value of the first data field “101010” has a mutingduty cycle of 40 ms which is 4 times of a CSI-RS transmission cycle of aserving cell (10 ms), and indicates that a muting subframe is present inthe second and fourth CSI-RS transmission cycle. (It is assumed that “0”means muting ON, and “1” means muting OFF) In addition, according to thecondition of the first step, since the muting offset is 3, this meansthat a fourth subframe (subframe number 3) in the second and fourthCSI-RS transmission cycle is a muting subframe.

In addition, since the second data field value is “000001”, thisindicates Pattern b in which the number of CSI-RS antenna ports of thecorresponding neighboring cell is 8 and which is the second patternamong 5 CSI-RS patterns in total illustrated in FIG. 3, among possible35 types of patterns in total (5 types of 8 antennas, 10 types of 4antennas, and 20 types of 2 antennas) when the second data field isbasically applied to both of FS1 (FDD) and FS2 (TDD) and is in the caseof a normal CP. (Patterns a to e with 8 antennas as illustrated in FIG.3 are indicated with “000000”, “000001”, “000010”, “00011”, and“000100”, and Patterns a to j with 4 antennas as illustrated in FIG. 4are indicated with “000101”, “000110”, “000111”, . . . , or the like, insequence)

It is assumed that the muting information as illustrated in FIG. 19considers only one neighboring cell. If the muting information isconfigured separately for two or more neighboring cells in a separatemanner, muting information corresponding to the number N of theneighboring cells is respectively generated.

FIG. 20 is a diagram illustrating a configuration of frames and resourcespaces indicating a state in which CSI-RSs of the actual serving cellare muted based on muting information of FIG. 19.

According to the muting information of FIG. 19, in the second and fourthCSI-RS transmission cycle, a fourth subframe (subframe number is 3)becomes a muting subframe and in the resource space in the subframe, REscorresponding to Pattern b of FIG. 3 (indicated with dark shadows inFIG. 20) become muting regions, and in the region, muting which isnon-allocation of data or zero power transmission is performed. This canbe indicated with a frame configuration diagram illustrated in FIG. 20.

FIG. 21 is a diagram illustrating a configuration of a channel stateacquiring apparatus using muting information according to the presentembodiment.

The channel information acquiring apparatus according to the presentembodiment acquires channel information by receiving a CSI-RS signalfrom two or more cells (base station). Generally, the channelinformation acquiring apparatus is realized in the user equipment or theUE, or in association with the same, but it is not limited thereto.

The channel state acquiring apparatus according to the presentembodiment may include a muting information receiver 2110 that receivesmuting information including a first data field indicating a muting dutycycle and an muting offset and a second data field indicating one ormore of a muting pattern group and a specific muting pattern in onemuting subframe from a serving cell among two or more cells, a CSI-RSreceiver 2120 that receives a CSI-RS signal in consideration of mutingfrom the serving cell and the neighboring cell, a muting regionidentifying unit 2130 that identifies a muting region where data is notreceived (or data with zero power is received) and a CSI-RS signal ofthe neighboring cell is transmitted with being muted, among the resourcespace (PDSCH) for data transmission in consideration of the mutinginformation; a channel state acquiring unit 2140 that acquires a channelstate by decoding the CSI-RS signal in consideration of the mutingregion.

The muting information received from the serving cell is informationindicating a region which is overlapped with CSI-RSs of a neighboringcell and to which data is not to be transmitted, and the mutinginformation can be configured with the first and second data fieldsdescribed in relation to FIGS. 2 to 16.

The muting information receiver 2110 performs a function of receivingmuting information which is generated and transmitted by the servingcell according to one or more combined methods among various methods inthe first to second steps described above, and the muting informationmay have a format as illustrated in FIG. 19 or the like, but the mutinginformation is not limited thereto.

The CSI-RS receiver 2120 performs a function of receiving a CSI-RSsignal from the serving cell and the neighboring cell, and the CSI-RSsignal received from the serving cell and the neighboring cell is areference signal (a CSI-RS of a serving cell) already generated in aregion allocated in the serving cell in order to transmit a CSI-RS or areference signal (a CSI-RS of a neighboring cell) generated in aresource region from neighboring cells corresponding to a region towhich muting is applied which implies non-transmission of data from aresource space (PDSCH) for data transmission of a serving cell so as tobe match with the muting information described above or zero powertransmission.

The muting region identifying unit 2130 performs a function ofidentifying a muting region for the serving cell using the mutinginformation received from the serving cell, and more specifically a stepof confirming a subframe in which a muting region is present byidentifying a muting duty cycle and a muting offset using a value of afirst data field of the received value of the muting information; a stepof deciding a muting pattern group and a specific muting pattern using avalue of a second data field in the corresponding muting subframe; and astep of deciding a muting region using a determined muting pattern or amuting pattern group. However, the muting region identifying unit is notlimited thereto, and the muting region may be identified according tothe principles as illustrated in FIGS. 19 and 20.

The channel state acquiring unit 2140 may acquire a channel state byperforming decoding in a manner of considering the muting region and notconsidering REs, which are muting regions, at the time of decoding datareceived from the serving cell by a user equipment, decoding CSI-RSs ofthe neighboring cells and a CSI-RS of the serving cell received fromresource regions of the neighboring cells corresponding to the mutedresource regions to decode a reference signal, and measuring a channelstate from the reference signal.

Accordingly, the efficiency of decoding of a CSI-RS may be improved, aCSI-RS of each cell can be correctly decoded by eliminating interventionfrom a CSI-RS of the neighboring cell, and therefore the correct channelestimation becomes possible.

In a configuration of muting information according to the presentembodiment and a technology of acquiring a channel state using thereof,all methods or technologies illustrated in FIGS. 2 to 16 can be used,and detailed description thereof is omitted to avoid an overlappeddescription.

FIG. 22 is a flowchart illustrating a detailed configuration relating tosteps of generating muting information according to another embodimentof the present invention.

The embodiment of FIG. 22 is different from the embodiment of FIG. 16 inthat the step of generating muting information in FIG. 15 includes afirst step S2205 of generating a first data field for determining andindicating a muting duty cycle and a muting offset, a second step S2210of generating a second data field for determining and indicating mutingpattern group information relating to one subframe, and a third stepS2215 of generating a third data field for determining and indicating aspecific muting pattern in the determined muting pattern group.

That is, in the embodiment of FIG. 16, muting information indicating amuting region to which data is not transmitted from a base station,which corresponds to a serving cell and performs zero power transmissionis configured by two steps in total. However, in the embodiment of FIG.22, the muting information is configured by 3 steps in total. Among the3 steps, the first step may be performed at the first time, but it maybe performed after the second and third steps are performed. Further,the information configured through the first to third steps is signaledto a user equipment (UE), and the corresponding cell performs mutingwhich indicates zero power transmission by not transmitting data to amuting pattern from each neighboring cell in a subframe corresponding toa muting offset per corresponding muting duty cycle based on the mutinginformation.

Herein below, the overall configurations of the first to third stepsconfiguring muting information, that is, the steps of configuring mutinginformation, the types of the configured information and the number ofbits will be described in detail.

However, in the embodiment of FIG. 22, the first step of determining amuting duty cycle and a muting offset and generating a first data fieldindicating the muting duty cycle and the muting offset is the same asthe first step in the embodiment of FIG. 16. Therefore, the descriptionthereof is omitted to avoid overlapping. Herein below, a descriptionwill be made only to detailed configurations relating to a second stepS2210 of generating a second data field for determining and indicatingmuting pattern group information for one subframe and a third step S2215of generating a third data field for determining and indicating aspecific muting pattern in the determined muting pattern group.

Second Step in the Embodiment of FIG. 22

Herein below, each case of the second step S2210 of generating a seconddata field for determining and indicating muting pattern groupinformation is described.

The second step means configuring a second data field for indicatingmuting pattern group in one subframe as muting information.

The muting pattern group is a pattern group including 8 REs like thecase of 8 CSI-RS antenna ports in a CSI-RS pattern. In a general casewhere the same application is performed to FS1 (Frame Structure 1, FDD)and FS2 (Frame Structure 2, TDD (excluding DwPTS of special subframe)),for a normal CP, when the number of CSI-RS antenna ports for onesubframe is 8 as illustrated in FIG. 3, 5 CSI-RS patterns in total aredefined, so the muting pattern group is one of 5 types. For an extendedCP, when the number of CSI-RS antenna ports for one subframe is 8 asillustrated in FIG. 7, 4 CSI-RS patterns in total are defined, so themuting pattern group is one of 4 types.

As in FIGS. 11 and 13, in FS2 (Frame Structure 2, TDD (excluding DwPTSof special subframe)), as to a CSI-RS pattern defined as an additionaloption, for a normal CP, when the number of CSI-RS antenna ports for onesubframe is 8, 3 CSI-RS patterns in total are defined, so the mutingpattern group is one of 3 types. For an extended CP, when the number ofCSI-RS antenna ports for one subframe is 8, 7 CSI-RS patterns in totalare defined, so the muting pattern group is one of 7 types.

In this case, a value of the second data field configuring the secondstep may be realized by dividing into two cases of “1)” and “2)” asdescribed below according to whether the communication system is basedon cell ID or a pattern group ID.

1) Based on Cell ID

In this case, the number of information bits configuring the second datafield may be 0 bit.

When cell IDs of neighboring cells an objects of muting are known (forexample, when neighboring cells as objects of muting consist of a CoMPset, and the CoMP sets know cell IDs of each other), CSI-RS patterns ofthe neighboring cells as objects of muting can be known based on thecell IDs (when CSI-RS patterns in the case of 8 CSI-RS antenna ports aredetermined based on the cell IDs). According to this, the muting patterngroups can be known per neighboring cell as an object of each muting.Therefore, in order to specify a muting pattern group, separateadditional data may not be required. The case of “2)” where a mutingpattern group is defined by a pattern group ID may be subdivided intotwo types, and these are defined as Methods 2-1 and 2-2.

2) Based on Pattern Group ID

2-1) Method 2-1

In this case, the number of information bits configuring the second datafield may be “the number N of neighboring cells as objects of muting×2to 3 bits”.

Method 2-1 relates to a case where CSI-RS patterns (relating to a caseof 8 antenna ports) of neighboring cells as objects of muting areconfigured based on pattern group IDs. That is, for a normal CP in ageneral case, 5 CSI-RS patterns in total for one subframe are definedwhen the number of CSI-RS antenna ports is 8 as illustrated in FIG. 3.Therefore, the muting pattern group is one of 5 types and muting patterngroups are named into pattern group IDs from 0 to 4 and transmitted with3 bits. (5 to 7 of the remaining bit values in the bit values of 3 bitsare reserved.)

For an extended CP in a general case, 4 CSI-RS patterns in total aredefined when the number of CSI-RS antenna ports for one subframe is 8 asillustrated in FIG. 7. Therefore, the muting pattern group is one of 4types and muting pattern groups are named into pattern group IDs from 0to 3 and transmitted with 2 bits.

As in FIGS. 11 and 13, in FS2 (Frame Structure 2, (excluding DwPTS ofspecial subframe)), as to a CSI-RS pattern defined as an additionaloption, for a normal CP, when the number of CSI-RS antenna ports for onesubframe is 8, 3 CSI-RS patterns in total are defined, so the mutingpattern group is one of 3 types. Therefore, muting pattern groups arenamed into pattern group IDs from 0 to 2 and transmitted with 2 bits. (3of the remaining bit value in the bit values of 2 bits are reserved.)For an extended CP, when the number of CSI-RS antenna ports for onesubframe is 8, 7 CSI-RS patterns in total are defined, so the mutingpattern group is one of 7 types. Therefore, muting pattern groups arenamed into pattern group IDs from 0 to 6 and transmitted with 3 bits. (7of the remaining bit value in the bit values of 3 bits are reserved.)The configured information can be respectively configured perneighboring cell as objects of muting.

In FS1 of the normal CP, only 5 patterns in a general case are present.Therefore, a method for configuring and transmitting the 5 patterns with3 bits has been described. In addition, in FS2, generally defined 5patterns and optionally defined 3 patterns are defined as differentcases, respectively. A method of transmitting the 5 patterns and the 3patterns with 3 bits and 2 bits respectively is described. However, thetwo cases are combined and 8 patterns in total are configured andtransmitted with 3 bits.

2-2) Method 2-2

In Method 2-2, the number of information bits configuring the seconddata field may be “the number N of neighboring cells as objects ofmuting×2 bits”.

In Method 2-2, a case of an additional option as in FIGS. 10 to 13 isnot considered, only general cases of FIGS. 2 to 9 are considered, andfor a normal CP as in FIG. 3, 5 CSI-RS patterns in total are definedwhen the number of CSI-RS antenna ports for one subframe is 8. At thistime, a CSI-RS pattern of the serving cell (a case of 8 antenna ports)is excluded, and there are 4 cases, and these are expressed with 2 bits.For example, when possible CSI-RS patterns in one subframe in total (acase of 8 antenna ports) are 5 of “a”, “b”, “c”, “d”, and “e”, and theCSI-RS pattern of the serving cell (a case of 8 antenna ports) is “c”,Pattern “d”, which is the next pattern becomes a muting pattern group ifthe bit value is “00”, Pattern “e”, which is the next pattern becomes amuting pattern group if the bit value is “01”, Pattern “a”, whichcyclically turns to the next pattern of Pattern “e” becomes a mutingpattern group if the bit value is “10”, and Pattern “b”, which is thenext pattern of Pattern “a” becomes a muting pattern group if the bitvalue is “11”.

In addition, as in FIG. 7, for an extended CP, when the number of CSI-RSantenna ports for one subframe is 8, 4 CSI-RS patterns in total aredefined. As to the 4 possible CSI-RSs, in the same manner as the case ofthe normal CP of the present method, a CSI-RS pattern of the servingcell (a case of 8 antenna ports) is excluded, and 3 muting patterngroups are configured as 2-bit information. Otherwise, a CSI-RS pattern(a case of 8 antenna ports) is not excluded, and 4 muting pattern groupsare configured as 2-bit information. The configured information can berespectively configured per neighboring cell as an object of muting.

Third Step in the Embodiment of FIG. 22

Herein below, a detailed configuration of the third step S2215 ofgenerating a third data field for determining and indicating a specificmuting pattern in the determined muting pattern group is described.

The third step is a process of configuring information on a concretespecific muting pattern to be substantially muted in consideration ofthe number of CSI-RS transmission antennas of a neighboring cell as anobject of muting after a muting pattern group in one subframe isidentified.

In this case, as in the second step, the field value configuring thethird data field may be 0 bit when a communication system is based on acell ID, or may be 3-bit information when a UE of the serving cell doesnot know a correct muting pattern of a neighboring cell as an object ofmuting in advance.

Herein below, a method of configuring the third data field will bedescribed by dividing into a case where a communication system is basedon a cell ID and a case where a UE of a serving cell does not know acorrect muting pattern of a neighboring cell as an object of muting.

1) Based on Cell ID

In this case, the number of bits configuring the third data field may be0 bits.

That is, a case where a cell ID of a neighboring cell as an object ofmuting is known in advance (for example, when neighboring cells asobjects of muting configures a CoMP set, and the CoMP sets know cell IDsof each other), and a case where patterns of the neighboring cells asobjects of muting can be known based on the cell IDs and the CSI-RSpattern is not a grouped pattern for a case of 8 antenna ports, butpatterns even for cases of 2 or 4 antenna ports are specifically known.That is, in the case where CSI-RS patterns for cases of 2, 4, and 8antenna ports are specifically determined based on cell IDs, not only amuting pattern group but also specific muting patterns per neighboringcell as an object of each muting can be known according to this.Therefore, additional data is not required for indicating a specificmuting pattern in a group according to the number of antenna ports.

2) A Case where a UE of a Serving Cell does not Know a Correct MutingPattern of a Neighboring Cell as an Object of Muting in Advance

In this case, the number of information bits configuring the third datafield may be 3 bits.

That is, in this method, when a UE in a serving cell does not know acorrect muting pattern of a neighboring cell as an object of muting inadvance, the serving cell should inform the corresponding UE of thecorrect muting pattern. That is, as to a muting group pattern determinedin the second step (regardless of the determined muting group pattern isbased on cell IDs or based on pattern group IDs), there will be onespecific muting pattern in the case of 8 antenna ports, 2 specificmuting patterns in the case of 4 antenna ports, and 4 specific mutingpatterns in the case of 2 antenna ports.

Therefore, 3-bit information is configured for the 7 cases in total. Theconfigured information can be respectively configured per neighboringcell as objects of muting.

The muting information generated as above may be transmitted by an upperlayer signaling such as RRC, may be dynamically transmitted by PDCCH inL1 layer, or may be signaled through MAC in L2 layer in some cases.

One or more of the cases described above may be selectively adoptedaccording to the specification of a communication system to which thepresent embodiment is applied for determining a muting region andgenerating muting information according to the present embodiment.

For example, depending on the type of the communication system, one ormore of various types for configuring first and second steps arecombined to configure the present invention.

In other words, the present invention may be configured not by adoptingall detailed types in the first to third steps described above, but bycombining one or more of various types configuring the first to thirdsteps according to a specification of a communication system, aconfiguration of a CSI-RS, a CSI-RS pattern, the number of CSI-RSantenna ports, a CSI-RS transmission cycle, a CSI-RS transmissionsubframe offset, or the like.

FIG. 23 is a flowchart illustrating a method for acquiring channelinformation in a user equipment using muting information according to anembodiment of FIG. 22.

The method for acquiring channel information according the presentembodiment is to acquire channel information by receiving a CSI-RSsignal from two or more cells (base station). Generally, the method isperformed in a user equipment or a UE, but the method is not limitedthereto.

The method for acquiring channel state according to the presentembodiment may include a step S2305 of receiving muting information froma serving cell among two or more cells, a step S2310 of receivingCSI-RSs in consideration of muting, a step S2315 of identifying a mutingregion in a resource space for data transmission of the serving cellusing the muting information and identifying a CSI-RS transmissionregion of the neighboring cell corresponding thereto, and a step S2320of acquring a channel state by decoding or estimating CSI-RSs of theserving cell or the neighboring cell in consideration of the mutingregion.

The muting information received from the serving cell in S2305 isinformation indicating a region which is overlapped with CSI-RSs of theneighboring cell and to which data is not to be transmitted, and themuting information can be configured with the first to third data fieldsdescribed in relation to FIGS. 2 to 15 and 22.

The steps S2305 and S2310 described above will be configured with itssequence changed, or realized with the steps combined into one.

A method for identifying the muting region in S2315 may include a stepof confirming a subframe in which a muting region is present byidentifying a muting duty cycle and a muting offset using a value of thefirst data field of the received muting information, a step ofdetermining a muting pattern group in the corresponding muting subframeusing a value of the second data field, a step of a specific mutingpattern in the corresponding muting pattern group using a value of thethird data field, and a step of determining a muting region using thedetermined muting pattern, but the method is not limited thereto.

The other steps of Steps S2310, 2320, and the like in FIG. 23 are thesame as the corresponding steps in FIG. 17 described above. Therefore,the description thereof is omitted to avoid overlapping.

In addition, when the embodiment in FIG. 22 is applied, theconfiguration of CSI-RS muting information transmission apparatus is thesame as the case in FIG. 18, but only the function of the mutinginformation generating unit 1830 will be different a little bit.

That is, when the embodiment of FIG. 22 is applied, the mutinginformation generating unit of the CSI-RS muting informationtransmission apparatus is to generate muting information that canindicate a muting region determined by the muting region determiningunit. In more detail, as described in relation to FIGS. 2 to 15 and 22,the muting information generating unit may generate final mutinginformation by generating and combining a first data field indicatingthe muting duty cycle and the muting offset, a second data fieldindicating muting pattern group information for one subframe, and athird data field indicating a specific muting pattern in the determinedmuting pattern group.

The first to third data field may be determined by a method of combiningone or more of various types of the first step as described above andthe second and third steps in the embodiment in FIG. 22, and thedetailed description thereof is omitted to avoid overlapping.

As an example of muting information according to an embodiment of FIG.22, it is assumed that a communication system to which the presentembodiment is applied has conditions as follows.

1) A condition of the first step: a case where the muting offset is thesame as the CSI-RS transmission offset of the serving cell (basestation) (it is assumed that the offset is 3), the muting duty cycle isa multiple of a CSI-RS transmission cycle of the serving cell (basestation), M=4, and signaling is separately performed with ┌log₂M┐=2about how many bits the number of information bits configuring the firstdata field are. (as a result, this corresponds to Method 2-1 of thefirst step described above, 6 bits in total)

2) A condition of the second step: a case where the step is performedbased on pattern group IDs, 5 CSI-RS patterns in total are defined whenthe number of CSI-RS antenna ports is 8, the muting pattern group is oneof five types, and among the patterns, Pattern “b” (indicated by “001”)is a muting pattern group. (corresponding to Method 2-1 of the secondstep described above, 3 bits in total)

3) A condition of the third step: a case where a UE of the serving celldoes not know the correct muting pattern of the neighboring cell as anobject of muting in advance, and the number of muting CSI-RS antennaports is 8 (indicated by “000” 3 bits in total) 1

In this condition, the muting information may include a bit value of afirst data field with 6 bits, and bit values of the second and thirddata field of 3 bits, respectively, and the muting information may beconfigured as in FIG. 24.

That is, FIG. 24 illustrates an example of data format of mutinginformation according to an embodiment of FIG. 22.

If it is assumed that the conditions of the first to third stepsdescribed above are satisfied, the muting information 2400 according tothe present embodiment includes a first data field region 2410 having 6bits of “101010”, a second data field region 2420 having 3 bits of“001”, and a third data field region 2430 having 3 bits of “000”.

The meaning of a value of each data field is described in detail asfollows. The value of a first data field having 6 bits of “101010” maybe divided into a 2-bit value (log₂M=2) of “10” indicating the number ofconfiguration bits (M=4) and a 4-bit region of “1010” indicating anactual muting duty cycle and an muting offset.

As a result, the value of the first data field of “101010” has a mutingduty cycle of 40 ms which is 4 times of a CSI-RS transmission cycle (10ms) of the serving cell (serving cell), and indicates that mutingsubframes are present in the second and fourth CSI-RS transmissioncycles. (if it is assumed that “0” means muting ON, and “1” means mutingOFF) In addition, according to the condition of the first step, themuting offset is 3, so it means that the fourth subframe (the subframenumber is 3) in the second and fourth CSI-RS transmission cycle is amuting subframe.

In addition, the value of the second data field of “001” indicates “b”which is a second pattern group among 5 CSI-RS patterns in total in FIG.3 in which the number of CSI-RS antenna ports is 8. (if it is assumedthat Pattern groups “a” to “e” are indicated by “000”, “001”, “010”,“011”, and “100”.)

In addition, since the value of the third data field is “000”, it meansthat the number of CSI-RS antenna ports is 8, and the final mutingpattern is determined as Pattern “b” of FIG. 3, not FIGS. 4 to 5.

It is assumed that the muting information as in FIG. 24 is inconsideration of only one neighboring cell, and if muting information isseparately configured per each of two or more neighboring cells, themuting information may be generated with a value multiplied by thenumber N of the neighboring cells.

The configuration of a frame and a resource space indicating a state inwhich CSI-RSs of an actual serving cell are muted based on mutinginformation of FIG. 24 is the same as FIG. 20 illustrated in relation toFIG. 19.

According to the muting information of FIG. 24, fourth subframes (thesubframe number is 3) in the second and fourth CSI-RS transmission cycleare muting subframes, and in the resource spaces of the subframes, REs(which are indicated with dark shadows in FIG. 20) corresponding toPattern “b” of FIG. 3 become muting regions, so muting which impliesnon-allocation of data and zero power transmission is performed in theregions. This is indicated with a frame configuration diagram asillustrated in FIG. 20.

In addition, though it is not illustrated, the configuration of channelstate acquiring apparatus using muting information according to theembodiment of FIG. 22 is the same as FIG. 21. However, the onlydifference is that the muting information received from the serving cellconfigures the first to third data field described in relation to FIGS.2 to 15 and 22.

In addition, the muting information receiver of the channel stateacquiring apparatus using the muting information according to theembodiment of FIG. 22 receives muting information generated by the firstto third steps described above, and the muting region identifying unitmay include a step of confirming a subframe in which a muting region ispresent by identifying a muting duty cycle and a muting offset using avalue of a first data field of the received muting information, a stepof deciding a muting pattern group in the corresponding muting subframeusing a value of a second data field in the corresponding mutingsubframe, a step of deciding a specific muting pattern in thecorresponding muting pattern group using a value of a third data field,and a step of deciding a muting region using a determined mutingpattern.

The other functions of channel state acquiring unit or the like are thesame as described in relation to FIG. 21. Therefore, the detaileddescription thereof is omitted to avoid overlapping. The use of theembodiments described above provides an effect of providing simple andeffective ways to reduce overhead to the maximum by configuring andtransmitting signaling information on a part for performing muting in aresource space of a CSI-RS signal to be transmitted to each userequipment by a base station according to each circumstances, that is,muting information, in consideration of CSI-RS patterns of neighboringcells configuring multicells such as a CoMP set, the number of CSI-RSantenna ports of each of the neighboring cells, a muting duty cycle(period or cycle) in time/frequency, an offset, and the like.

In addition, there is an effect of allowing for correct CSI-RS decodingand therefore precisely performing channel state estimation since aserving cell in a multicell environment generates and transmits CSI-RSsof which regions overlapped with CSI-RSs of the neighboring cell aremuted.

Even if it was described above that all of the components of anembodiment of the present invention are coupled as a single unit orcoupled to be operated as a single unit, the present invention is notnecessarily limited to such an embodiment. That is, among thecomponents, one or more components may be selectively coupled to beoperated as one or more units. In addition, although each of thecomponents may be implemented as an independent hardware, some or all ofthe components may be selectively combined with each other, so that theycan be implemented as a computer program having one or more programmodules for executing some or all of the functions combined in one ormore hardwares. Codes and code segments forming the computer program canbe easily conceived by an ordinarily skilled person in the technicalfield of the present invention. Such a computer program may implementthe embodiments of the present invention by being stored in a computerreadable storage medium, and being read and executed by a computer. Amagnetic recording medium, an optical recording medium, a carrier wavemedium, or the like may be employed as the storage medium.

In addition, since terms, such as “including,” “comprising,” and“having” mean that one or more corresponding components may exist unlessthey are specifically described to the contrary, it shall be construedthat one or more other components can be included. All of theterminologies containing one or more technical or scientificterminologies have the same meanings that persons skilled in the artunderstand ordinarily unless they are not defined otherwise. A termordinarily used like that defined by a dictionary shall be construedthat it has a meaning equal to that in the context of a relateddescription, and shall not be construed in an ideal or excessivelyformal meaning unless it is clearly defined in the presentspecification.

Although a preferred embodiment of the present invention has beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims. Therefore, the embodimentsdisclosed in the present invention are intended to illustrate the scopeof the technical idea of the present invention, and the scope of thepresent invention is not limited by the embodiment. The scope of thepresent invention shall be construed on the basis of the accompanyingclaims in such a manner that all of the technical ideas included withinthe scope equivalent to the claims belong to the present invention.

The invention claimed is:
 1. A method for transmitting CSI-RS mutinginformation reflecting CSI-RS intervention of a neighboring cell to auser equipment by a specific cell in a multicell environment, the methodcomprising: receiving CSI-RS information of the neighboring cellincluding at least one of a CSI-RS pattern, the number of CSI-RS antennaports, a CSI-RS transmission cycle (duty cycle), CSI-RS transmissionsubframe offset information, from the neighboring cell; determining amuting region which is a time/frequency resource region that overlapswith a CSI-RS of the neighboring cell and therefore requires mutingbased on the CSI-RS information of the neighboring cell; generating themuting information including a first data field that indicates a cycleand an offset of muting subframes, each of which includes the mutingregion, and a second data field that indicates a specific muting patternin which muting is to be performed in the muting subframes and has onebit number among 12 bits to 28 bits, which indicates, in a bitmapformat, whether to apply muting, and transmitting the generated mutinginformation to the user equipment.
 2. The method for transmitting CSI-RSmuting information as claimed in claim 1, wherein the first data fieldis configured based on locations of the muting subframes to which themuting is applied and a relation between CSI-RS transmission cycles andCSI-RS transmission offset of the specific cell or the neighboring cell.3. The method for transmitting CSI-RS muting information as claimed inclaim 1, wherein the second data field has one bit number among 12 bitsto 28 bits, which indicates, in a bitmap format, whether to applymuting, with respect to resource elements corresponding to each CSI-RSpattern that can be transmitted in a specific number of antenna ports.4. The method for transmitting CSI-RS muting information as claimed inclaim 1, wherein the second data field is configured by 16 bit valuesfor indicating each CSI-RS pattern to be muted based on the specificnumber of antenna ports.
 5. The method for transmitting CSI-RS mutinginformation as claimed in claim 1, wherein the second data field mayindicate a muting pattern group in addition to a muting pattern, themuting pattern group is configured based on a specific number of antennaports, and resource regions that belong to the muting pattern group areall muted regardless of the number of antenna ports of the neighboringcell substantially transmitting CSI-RSs.
 6. A method for acquiring achannel state of each cell after receiving CSI-RSs from two or morecells by a receiver, the method comprising: receiving muting informationincluding a first data field that indicates a cycle and an offset ofmuting subframes from a serving cell out of two or more cells and asecond data field that indicates a specific muting pattern in whichmuting is to be performed in the muting subframes and has one bit numberamong 12 bits to 28 bits, which indicates, in a bitmap format, whetherto apply muting; receiving CSI-RSs of the neighboring cell transmittedfrom a resource region of a neighboring cell corresponding to a partialregion muted based on the muting information in a resource space fortransmitting CSI-RSs of the serving cell and data of the serving cell;identifying a muting region in a resource space for transmitting data ofthe serving cell using the muting information and identifying a regionfor transmitting the CSI-RSs of a neighboring cell correspondingthereto; and acquiring a channel state by decoding the CSI-RSs of theserving cell and the neighboring cell considering the muting region. 7.An apparatus for transmitting CSI-RS muting information, comprising: aneighboring cell information receiver that receives, from one or moreneighboring cells in a multicell environment, CSI-RS information of theneighboring cells including at least one of CSI-RS patterns, the numberof CSI-RS antenna ports, CSI-RS transmission cycles (Duty Cycle), andCSI-RS transmission subframe offset information; a muting regiondetermining unit that determines a muting region which is atime/frequency resource region that overlaps with a CSI-RS of theneighboring cell and therefore requires muting in a resource space fortransmitting data of a serving cell based on the CSI-RS information ofthe neighboring cell; a muting information generating unit thatgenerates muting information including a first data field whichindicates the muting region and indicates a cycle and an offset ofmuting subframes and a second data field which indicates a specificmuting pattern to be muted in the muting subframes and has one bitnumber among 12 bits to 28 bits, which indicates, in a bitmap format,whether to apply muting; and a muting information transmitter thattransmits the generated muting information to a user equipment (UE). 8.An apparatus for acquiring a channel state of each cell after a receiverreceives CSI-RSs from two or more cells, the apparatus comprising: amuting information receiver that receives muting information including afirst data field that indicates a cycle and an offset of mutingsubframes from a serving cell out of two or more cells and a second datafield that indicates a specific muting pattern in which muting is to beperformed in the muting subframes and has one bit number among 12 bitsto 28 bits, which indicates, in a bitmap format, whether to applymuting; a CSI-RS receiver that receives CSI-RS signals of theneighboring cell transmitted from a resource region of a neighboringcell corresponding to a partial region muted based on the mutinginformation in a resource space for transmitting CSI-RSs of the servingcell and data of the serving cell; a muting region identifying unit thatidentifies a muting region in a resource space for transmitting data ofthe serving cell using the muting information and identifies a resourceregion for transmitting CSI-RSs of a neighboring cell correspondingthereto; and a channel state acquiring unit that acquires a channelstate by decoding the CSI-RS signals of the serving cell and theneighboring cell considering the muting region.